Frequency of systematic reactions to penicillin skin tests.

BACKGROUND: Penicillin skin testing is generally considered to be safe when performed sequentially with puncture and intradermal testing although fatalities have been reported. OBJECTIVE: We analyzed the rate of systemic reactions to penicillin skin tests for a period of seven and two-thirds years. METHOD: This retrospective study used a computerized database at the Mayo Clinic. Altogether 1710 patients were skin-tested to penicillin from January 1992 to September 1999. All patients tested had a history of penicillin allergy. Patients were tested with benzylpenicilloyl polylysine (Pre-Pen) (6.0 X 10(-5) M), freshly prepared penicillin G (10,000 units/ml), and penicilloate (0.01 M). Prick tests were done first and if negative then intradermal tests. Systemic reactions were evaluated and treated by physicians. RESULTS: Eighty-six patients had positive penicillin skin tests of which two had systemic reactions. Our systemic reaction rate for all patients tested was 0.12%; and 2.3% for the penicillin skin test-positive group, with no fatalities. CONCLUSION: The incidence of systemic reaction to penicillin skin tests is low. Skin prick tests should always be done first. If there is a history of a previous serious reaction, the skin tests-if done-should be diluted to start with. Those doing penicillin skin tests should be prepared to treat a systemic reaction.     

Lack of allergic cross-reactivity to cephalosporins among patients allergic to penicillins

There are some contradicting data about clinical allergic cross-reactivity to cephalosporins among patients who have had a previous allergic reaction to penicillins. The purpose of this study was to assess the safety of administering cephalosporins to penicillin-allergic patients. The diagnosis of penicillin allergy was made by positive skin tests to penicillin reagents and/or provocation tests with the penicillin suspected of causing the allergic reaction. To assess the clinical tolerance to cephalosporins, 41 well-characterized penicillin allergic patients diagnosed by positive skin tests and/or provocation tests were challenged with three cephalosporins that do not share the same side chain to the penicillin that induced the reactions: cephazoline, cefuroxime and ceftriaxone. Skin prick and intradermal tests with all cephalosporins tested were negative. All penicillin-allergic patients tolerated therapeutic doses of the three cephalosporins tested (cephazoline, cefuroxime and ceftriaxone) without any ill effect. These results indicate that the risk of suffering from an allergic reaction on administering cephalosporins to penicillin-allergic patients seems to be very low, provided that cephalosporins with a different side chain to the penicillin responsible for the allergic reaction are used.     

Diagnosing nonimmediate reactions to penicillins by in vivo tests

BACKGROUND: Maculopapular and urticarial rashes are nonimmediate manifestations common during penicillin treatment; the former often represent cell-mediated hypersensitivity. Our objectives were to assess the incidence of allergy in adults reporting nonimmediate manifestations during penicillin therapy and to evaluate the diagnostic potential of patch tests, delayed-reading skin tests and challenges in such cases. METHODS: We used prick and intradermal tests as well as patch tests with penicillin determinants, ampicillin, amoxicillin and any other suspect penicillins. We also performed challenges with the suspect antibiotics. RESULTS: Such antibiotics were aminopenicillins in 93.1% of 259 patients, most of whom had suffered from maculopapular rashes followed by piperacillin (4.2%). Three subjects displayed immediate skin test positivity. Ninety-four subjects showed patch test and delayed intradermal test positivity to the culprit penicillin (90 to aminopenicillins and 4 to piperacillin) and were considered as having had delayed hypersensitivity reactions. Five of the 8 subjects who displayed delayed intradermal test positivity and patch test negativity to the suspect penicillin underwent challenges, 2 reacted positively to the responsible aminopenicillin. Among the remaining 154 with negative results in allergologic tests, 125 agreed to undergo challenges; only 3 reacted. In all, 98 patients -- 93 of whom had experienced maculopapular rashes -- displayed delayed hypersensitivity (94 to aminopenicillins and 4 to piperacillin). CONCLUSIONS: Both patch and intradermal tests are useful in evaluating nonimmediate reactions to penicillins, particularly maculopapular rashes. Patch test and delayed intradermal positivity together indicate delayed hypersensitivity. Intradermal testing appears to be slightly more sensitive than patch testing.     

Skin testing in patients with hypersensitivity reactions to iodinated contrast media – a European multicenter study

Background:  Iodinated contrast media cause both immediate and nonimmediate hypersensitivity reactions. The aim of this prospective study was to determine the specificity and sensitivity of skin tests in patients who have experienced such reactions.
Methods:  Skin prick, intradermal and patch tests with a series of contrast media were conducted in 220 patients with either immediate or nonimmediate reaction. Positive skin tests were defined according to internationally accepted guidelines. Seventy-one never-exposed subjects and 11 subjects who had tolerated contrast medium exposure, served as negative controls.
Results:  Skin test specificity was 96–100%. For tests conducted within the time period from 2 to 6 months after the reaction, up to 50% of immediate reactors and up to 47% of nonimmediate reactors were skin test positive. For immediate reactors, the intradermal tests were the most sensitive, whereas delayed intradermal tests in combination with patch tests were needed for optimal sensitivity in nonimmediate reactors. Contrast medium cross-reactivity was more common in the nonimmediate than in the immediate group. Interestingly, 49% of immediate and 52% of nonimmediate symptoms occurred in previously unexposed patients. Many of these patients were skin test positive, indicating that they were already sensitized at the time of first contrast medium exposure.
Conclusions:  These data suggest that at least 50% of hypersensitivity reactions to contrast media are caused by an immunological mechanism. Skin testing appears to be a useful tool for diagnosis of contrast medium allergy and may play an important role in selection of a safe product in previous reactors.     

Skin testing to detect penicillin allergy

Skin testing for penicillin allergy with penicillin G (Pen G), penicilloic acid (PA), and penicilloyl poly-L-lysine (PPL) was performed on 740 subjects, and the results were assessed from epidemiologic and immunologic perspectives. Approximately 95% of these patients had histories of apparent allergic reactions to beta-lactam antibiotics, and 63% were skin-test positive. The prevalence of positive skin tests was related to the time that had elapsed between clinical reactions and skin testing. Ninety-three percent were skin-test positive 7 to 12 mo after reactions, and 22% were positive 10 yr or more after reactions. Patients under 30 yr of age had a prevalence of positive skin tests 1.7-fold higher than older patients. Testing with PPL, PA, and Pen G detected 76.3%, 55.3%, and 57.1% of the positive patients, respectively. Omission of PPL, PA, or Pen G would have led to a failure to detect 25.6%, 7.2%, and 6.2% of the positive patients, respectively. Subjects with skin tests positive to penicillin often reacted to skin tests with other beta-lactam antibiotics; 73% (41 of 56) reacted to ampicillin and 51% (38 of 74) reacted to cephalothin. No serious allergic reactions were provoked by testing. None of the 83 skin test--negative patients treated with beta-lactam antibiotics immediately after testing experienced acute allergic reactions. Two patients developed mild urticaria beginning 3 and 5 days into therapy. One skin test--negative patient experienced urticaria 3 hr after receiving oral penicillin 6 mo after skin testing. This patient's skin-test status immediately before therapy was unknown. These results support the position that testing with PPL, PA, and Pen G is a rapid, safe, and effective method for identifying patients at risk, or not at risk, for allergic reactions to penicillin.     

Evaluation of adverse reactions to local anesthetics: experience with 236 patients.

BACKGROUND: Adverse reactions to local anesthetics (LAs) are frequently reported. Although most of these reactions are not immune mediated, many patients are referred to allergy clinics and undergo extensive evaluation. OBJECTIVE: To determine the prevalence of true LA allergy among the patients referred for suspected hypersensitivity and to evaluate the usefulness of the currently used evaluation protocol. METHODS: A total of 236 patients referred to our allergy clinic for investigation of LA hypersensitivity were included in this study. The evaluation protocol was composed of skin prick and intradermal tests, followed by subcutaneous challenge with unrelated LA preparations that contained preservatives. RESULTS: Skin prick and intradermal test results were negative for all subjects. No objective adverse reactions were observed during the challenge in all but 1 patient, who developed local erythema at the site of injection and later underwent an uneventful challenge with a different LA. CONCLUSIONS: Allergic reactions were not reproduced during testing and challenge with LA preparations that contained preservatives or preservatives with adrenaline in our large group of patients with suspected LA allergy. Since both prick and intradermal skin test results were negative in all the patients and did not provide us with useful information, we propose to modify the standard protocol by omitting intradermal tests and shortening the challenge. We also suggest that the whole procedure be performed with LAs that contain preservatives, which are usually the preferred preparations widely used in daily practice.     

Effect of topical vapocoolant spray on skin test wheal, flare, and pain responses.

BACKGROUND: Skin puncture and intradermal tests are commonly used to evaluate allergic rhinitis. Ethyl chloride, a topical vapocoolant spray, provides skin analgesia before venipuncture, but it has not been studied with allergy skin testing. Objective: To determine the effects of ethyl chloride vs placebo on skin puncture testing (SPT) and intradermal allergy testing. METHODS: We enrolled 20 healthy adults with a history of positive aeroallergen skin test results in a randomized, double-masked, placebo-controlled study. Ethyl chloride and placebo sprays were randomly placed on the upper back. Paired SPT was performed with saline, histamine, and standardized aeroallergens, including Bermuda grass, Kentucky blue grass, timothy grass, cat, Dermatophagoides pteronyssinus, and Dermatophagoides farinae. Serial dilutional end-point intradermal tests were then performed using 1 standardized aeroallergen. Wheal and flare areas were outlined, scanned, and digitally measured. Participants used a 10-cm visual analog scale to record pain during skin testing. RESULTS: Eighteen individuals completed the study. Compared with placebo, ethyl chloride had no significant effect on histamine wheal (P = .53), histamine flare (P = .39), aeroallergen wheal (P = .10), or aeroallergen flare (P = .71) area for SPT. Serial dilutional end-point intradermal testing was similar after ethyl chloride and placebo application (P = .75). Mean pain scores for SPT were improved with ethyl chloride compared with paired placebo skin tests, although pain scores did not reach significance for SPT (P = .21) or intradermal testing (P = .87). CONCLUSIONS: Ethyl chloride does not significantly reduce histamine and aeroallergen wheal and flare areas during SPT and intradermal allergy skin testing. Ethyl chloride, vs placebo, reduced pain in some individuals during skin testing, although this did not attain statistical significance.     

Cephalosporin allergy

Allergic reactions to cephalosporins may occur because of sensitization to cephalosporin determinants shared with penicillin or to unique cephalosporin haptens. The exact nature of the haptenic determinants resulting from the degradation of currently available cephalosporins is incompletely understood. Cephalosporin skin testing or specific IgE immunoassays have limited clinical utility. Patients with a history of allergy to cephalosporins or penicillin may be at increased risk for a reaction to cephalosporins. Skin testing for an allergy to penicillin may be helpful in patients with a history of penicillin allergy who have a clinical indication for cephalosporin use. Most of these patients have negative tests and should not be at increased risk for a reaction to cephalosporins.     

Evaluation of penicillin hypersensitivity: Value of clinical history and skin testing with penicilloyl-polylysine and penicillin G : A cooperative prospective study of the penicillin study group of the American Academy of Allergy

A multicenter cooperative study of almost 3,000 patients by members of the Penicillin Study Group of the American Academy of Allergy has confirmed the usefulness of skin tests to penicillin G (Pen G) and penicilloyl-polylysine (PPL) in the evaluation of penicillin hypersensitivity. Nineteen percent of 1,718 patients with a history of penicillin allergy had positive skin tests to either or both agents, vs 7% of 1,229 patients with no such history. Among patients with a history of penicillin allergy where a detailed history was available, positive skin tests were noted in 46% with a history of anaphylaxis, 17% with a history of urticaria or angioneurotic edema, and 7% with a history of a maculopapular reaction. PPL Generally gave somewhat higher reaction rates than Pen G, but both skin tests were needed to elicit the maximum number of reactors. After skin tests were completed, 379 patients were challenged with penicillin. Six percent of patients with a positive history had an allergic reaction vs 2% of patients with a negative history. However, 67% of the 9 challenged patients with a positive skin test had an allergic reaction, and half of these were immediate or early systemic reactions. Only 3% of the 346 challenged patients with a negative skin test had a reaction to challenge and only one fourth of these had early reactions thought to be possibly mediated by IgE.     

Cross-reactivity and tolerability of imipenem in patients with delayed-type, cell-mediated hypersensitivity to β-lactams

Background:  Administration of imipenem-cilastatin to patients with IgE-mediated hypersensitivity to β-lactams has always been considered potentially harmful. Recent studies have demonstrated the tolerability of carbapenems (imipenem-cilastatin and meropenem) in patients with IgE-mediated hypersensitivity to β-lactams; there are no studies on this topic regarding patients with cell-mediated allergy to β-lactams. The aim of this study is to assess cross-reactivity and tolerability of imipenem in patients with cell-mediated allergy to β-lactams.
Methods:  From our database we selected 73 patients with cell-mediated allergy to β-lactams, diagnosed by means of immediate-type skin tests, delayed reading intradermal tests, patch tests and detection of specific IgE. Patients with negative patch tests with imipenem-cilastatin underwent an intramuscular test dosing.
Results:  Our patients had a total of 94 nonimmediate reactions to penicillins. All patients had positive patch tests and/or delayed reading intradermal tests for at least one of the penicillin reagent tested and negative immediate-type skin tests and specific IgE. Four patients out of 73 had a positive patch tests to at least one penicillin reagent and imipenem-cilastatin showing cross-reactivity. Sixty-four patients underwent the imipenem-cilastatin intramuscular test dosing and none of them had a clinical reaction.
Conclusions:  Our rate of cross-reactivity between imipenem-cilastatin and other β-lactams was 5.5%. This result is different from previous findings and this may be explained by the fact that we investigated patients with cell-mediated allergy to β-lactams. Patients with cell-mediated allergy to β-lactams should undergo patch tests and a tolerance challenge test before treatment with imipenem-cilastatin.     

Diagnosis of penicillin allergy by means of Phadebas RAST® penicilloyl G and V and skin tests

Fifty patients with suspected allergy to penicillin were tested. Skin tests were done with Na-penicillin G and penicilloyl-polylysin. Specific IgE antibody assays were done with penicilloyl G and V conjugates by means of RAST. The overall agreement between skin test and RAST results was 87%, borderline cases not included. In one case, skin tests were positive to penicillamine only, while RAST for penicilloyl G and V both proved to be positive. One case of penicillin allergy could be diagnosed in vitro post mortem only. Two cases of Hoigné syndrome showed no evidence of allergy. Patterns of skin manifestations varied but urticaria was the most commonly seen feature. Twenty patients without adverse reactions to penicillin treatment and seven patients who had not received penicillin over the last 10 years served as controls. None of them were positive in either skin tests or RAST. Two of our twenty control patients developed penicillin allergy during the study. Both showed positive RAST results.     

Skin and serologic testing in the diagnosis of latex allergy

Background: Latex hypersensitivity is associated with occupational allergy contact urticaria, rhinitis, asthma, and anaphylaxis. However, standardized sensitive and specific latex extract for skin prick or serologic testing is not available in the United States.Methods: We investigated the reliability of two latex extracts in 118 consecutive skin tests in patients with spina bifida, health care workers, and other patients with symptoms of latex allergy, and 10 control subjects.Results: Forty-two of 86 patients with spina bifida, 11 of 15 health care workers with symptoms of latex allergy, 6 of 7 patients with symptoms of latex allergy, and 0 of 10 control subjects had demonstrable immediate wheal and flare responses to latex prick testing. In addition, 95 patients and 10 control subjects were tested concurrently for latex-specific IgE by ELISA. Of 55 patients with positive skin prick test results, 48 were reactive as determined by ELISA for IgE-specific latex antibody (sensitivity = 87%). Latex ELISA titers were significantly higher in patients with positive skin prick test results with a history of anaphylaxis to latex and in individuals without symptoms of latex allergy who had positive skin prick test results when compared with patients with negative skin prick test results. During the skin test procedure, nine patients had adverse reactions, including anaphylactic reactions in four.Conclusions: Skin prick and serum testing are reliable methods of diagnosing latex allergy. Serologic evaluation may be more desirable until allergen standardization is available.     

Skin testing as a biomarker in drug allergy

Despite the significant negative impact drug allergies can have on patient care, the diagnosis is largely based on clinical history, and there are limited diagnostic tests that can be done at the time of a reaction. Biomarkers are needed to improve the diagnosis and the identification of the culprit medication. Skin testing is the most useful biomarker for immediate- and delayed-type reactions available, but it is limited by its low sensitivity. To improve its accuracy and reproducibility, a standardized procedure must be used. For immediate-type reactions, penicillin skin testing is the most widely studied, and it can be used in patients with history of anaphylaxis or recent immunoglobulin E-mediated reaction or for whom there is a significant risk if a reaction were to occur, such as pregnancy. Skin testing is also important in allergy to platinum agents allowing for continued first-line therapy. For delayed-type reactions, patch testing and delayed intradermal testing, used in conjunction with clinical history, can help to improve identification of the culprit medication depending on the type of reaction. Other biomarkers including in vitro testing for specific immunoglobulin E, basophil activation test, lymphocyte transformation test, ELISpot, and genetic factors that increase the likelihood of reaction are under investigation, and they may be most helpful when used in combination with the clinical history and skin testing results.     

Diagnosis of iodinated contrast media hypersensitivity: results of a 6-year period

Background Iodinated contrast media (ICM) hypersensitivity reactions represent a serious problem. Very few clinical data concerning systematic skin testing to ICM are available. Objective To evaluate the utility of ICM skin testing in patients with ICM hypersensitivity. Material and methods All patients referred over a 6‐year period for ICM hypersensitivity past reactions were skin tested for (a) the implicated ICM, or (b) a set of ICM if they were positive for the implicated ICM or if its name was unknown. Results Forty‐four patients, with a median age of 56 years, were studied (15 males, 29 females). The ICM skin tests were positive in 10 patients (23%): one had a positive skin prick test, seven an immediate positive intradermal test (IDT) and two a delayed positive IDT. Skin tests were more often positive in patients with immediate (9/32) as compared with those with non‐immediate reactions (1/11). The time interval between the reaction and skin testing was shorter for those patients with an immediate ICM reaction and a positive skin test result (3 months [2.5–174.0]) as compared with those with an immediate ICM reaction and a negative skin test (48 months [6.8–159.0]), (P<0.05). Respiratory allergy was more frequent in the positive group (6/10 vs. 7/34, P<0.05). Conclusions Skin tests with ICM are positive in a subgroup of patients with ICM hypersensitivity and may play an important role in the diagnosis of ICM allergy.     

Tolerability of meropenem in children with IgE-mediated hypersensitivity to penicillins

Background:  Administration of meropenem to penicillin-allergic patients who might benefit from this treatment is usually avoided because of a 47.4% rate of cross-reactivity to imipenem, the prototype of the carbapenem class of β-lactam antibiotics, demonstrated in a single study on the basis of positive responses to skin tests with imipenem reagents. However, recent studies of ours have demonstrated a very low rate of cross-reactivity between penicillins and both meropenem and imipenem in adults.
Objective:  To assess cross-reactivity and tolerability of meropenem in children with documented penicillin allergy.
Methods:  One hundred and eight consecutive children who had suffered a total of 129 immediate reactions (120 urticarial and/or angioedematous manifestations and 9 anaphylactic shocks) to penicillins and had positive results to skin tests for at least one of the penicillin reagents tested underwent skin tests with meropenem and negative subjects were challenged with it.
Results:  One subject (0.9%) displayed a positive intradermal test to meropenem. The remaining 107 subjects with negative skin tests to meropenem tolerated challenges. Challenges were not followed by full therapeutic courses.
Conclusions:  Our results demonstrate a low rate of cross-reactivity between penicillins and meropenem. Therefore, the practice of avoiding meropenem in children with immunoglobulin E-mediated hypersensitivity could be abandoned; in those who especially require meropenem treatment, prophylactic skin tests are advisable, because negative results indicate tolerability.     

* Immediate allergic reactions to amoxicillin

A large group of patients with suspected allergic reactions to (β-lactam antibiotics was evaluated. A detailed clinical history, together with skin tests, RAST (radioallergosorbent test), and controlled challenge tests, was used to establish whether patients allergic to β-lactam antibiotics had selective immediate allergic responses to amoxicillin (AX) or were cross-reacting with other penicillin derivatives. Skin tests were performed with benzylpenicilloyl-poly-L-lysine (BPO-PLL), benzylpenicilloate, benzylpenicillin (PG), ampicillin (AMP), and AX. RAST for BPO-PLL and AX-PLL was done. When both skin test and RAST for BPO were negative, single-blind, placebo-controlled challenge tests were done to ensure tolerance of PG or sensitivity to AX. A total of 177 patients were diagnosed as allergic to β-lactam antibiotics. We selected the 54 (30.5%) cases of immediate AX allergy with good tolerance of PG. Anaphylaxis was seen in 37 patients (69%), the other 17 (31%) having urticaria and/or angioedema. All the patients were skin test negative to BPO; 49 of 51 (96%) were also negative to MDM, and 44 of 46 (96%) to PG. Skin tests with AX were positive in 34 (63%) patients. RAST was positive for AX in 22 patients (41%) and to BPO in just 5 (9%). None of the sera with negative RAST for AX were positive to BPO. Challenge tests with AX were performed in 23 subjects (43%) to establish the diagnosis of immediate allergic reaction to AX, and in 15 cases (28%) both skin test and RAST for AX were negative. PG was well tolerated by all 54 patients. We describe the largest group of AX-allergic patients who have tolerated PG reported so far. Diagnosis of these patients can be achieved only if specific AX-related reagents are employed. Further studies are necessary to determine the exact extent of this problem and to improve the efficacy of diagnostic methods.     

Penicillin resensitization among hospitalized patients

The purpose of this study was to determine the frequency of resensitization to penicillin after oral or intravenous treatment with beta-lactam antibiotics in hospitalized patients with histories of penicillin allergy. Seventeen adults (aged 24 to 76 years) and one child (aged 10 years) were treated intravenously and/or orally with beta-lactam antibiotics after negative skin tests were obtained with benzylpenicilloyl polylysine, potassium penicillin G, and alkaline hydrolysis products of penicillin G as minor determinant mixture. Repeat skin testing was performed 1 to 12 months after the therapy. Three patients (16%) became skin test positive after the treatment. Two patients reacted to potassium penicillin G alone, and the other patient reacted to benzylpenicilloyl polylysine and minor determinant mixture. These three patients were among the 15 patients who were treated with intravenous antibiotics. This study reveals a high percentage of skin test conversion after intravenously administered penicillin therapy and confirms the present practice of advising patients with a history of penicillin allergy who have successfully completed penicillin treatment to have a repeat skin test before future exposure to beta-lactam antibiotics.     

Diagnosis and Immunotherapy of Mould Allergy

To determine reproducibility and the optimal way of expressing skin sensitivity, simultaneous skin prick tests (SPT) and intradermal tests (ICT) were performed on 25 mould-allergic patients. The patients had a well-documented history of allergy to Cladosporium and Alternaria and were tested with partially purified standardized extracts of these two mould species. Skin prick tests were carried out on the volar side of the forearm and intradermal tests on the backs of the patients. The skin tests were performed as titration using quadruplicate determinations of 10-fold allergen dilutions. The area of the skin reactions measured by planimetry were plotted in a log-log system as a function of the allergen concentration. The reproducibility (SD/mean area X 100%) of the ICTs was significantly higher than that of the SPTs (17% versus 29%). A very low reproducibility was found with wheal areas less than 5 mm2. The dose response curve of the SPT wheal area was steeper than that obtained with ICT, both concerning ICT wheal and flare. Increasing the allergen concentration with a factor 10 resulted in a doubling of the wheal area in SPT, in contrast to a factor 1.7 using ICT. The coefficient of correlation using linear regression on the dose response curve was always higher than 0.9 with SPT and ICT wheal, but significantly lower with ICT flare. Skin sensitivity was estimated as end-point and histamine equivalent reaction. No significant correlation between SPT and ICT end-point titration was found contrary to the histamine equivalent reaction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elective penicillin skin testing in a pediatric outpatient setting.

BACKGROUND: Adverse reactions associated with penicillin-type antibiotics are common in pediatric practice, leading to the subsequent unnecessary use of alternative antibiotics. IgE-mediated penicillin allergy represents only a fraction of these adverse reactions. OBJECTIVES: To examine (1) the trend of penicillin skin test reactivity during a recent 10-year interval, (2) the relative distribution of specific reagents related to a positive skin test result, and (3) skin test reactivity as a function of reaction history. METHODS: Penicillin testing using 3 reagents--benzylpenicilloyl polylysine, penicillin G, and sodium penicilloate (penicillin A)--was conducted in a prospective study of 359 consecutive patients referred to an outpatient pediatric allergy clinic between January 1, 1993, and May 31, 2003. We also retrospectively reviewed penicillin skin test results for 562 children previously tested between January 1, 1979, and December 31, 1992. RESULTS: Between 1993 and 2003, the prevalence of penicillin skin test sensitivity markedly declined. Of all the positive skin test results between 1979 and 2002, either penicillin G or sodium penicilloate or both identified 34%, with sodium penicilloate alone responsible for 8.5%. The rate of positive skin test reactions was not significantly different between patients with vs without a history of suggestive IgE-mediated reactions. CONCLUSIONS: A marked decline in penicillin skin test sensitivity in the pediatric age group is identified. The minor determinant reagents penicillin G and sodium penicilloate are both necessary for determining potential penicillin allergy. Relating history alone to potential penicillin sensitivity is unreliable in predicting the presence or absence of a positive skin test result.