From the Guidelines
To treat a penicillin rash, stop taking the penicillin medication immediately and contact your healthcare provider. For mild symptoms, take an antihistamine like diphenhydramine (Benadryl) 25-50mg every 6 hours or cetirizine (Zyrtec) 10mg daily to reduce itching, as suggested by recent guidelines 1. Apply a topical hydrocortisone cream (0.5-1%) to affected areas 2-3 times daily for up to a week to decrease inflammation. Cool compresses and lukewarm oatmeal baths can provide additional relief. Avoid scratching to prevent infection. If you experience severe symptoms like difficulty breathing, facial swelling, or dizziness, seek emergency medical attention as these indicate a serious allergic reaction, which can be fatal if not treated promptly 1.
The rash occurs because your immune system identifies penicillin as a threat and releases histamine, causing inflammation and itching. After recovery, inform all healthcare providers about your penicillin allergy to prevent future exposure, and consider wearing a medical alert bracelet. It is essential to note that penicillin skin testing with the major and minor determinants of penicillin can reliably identify persons at high risk for penicillin reactions 1. However, the management of penicillin allergy should be individualized, and the decision to use penicillin should be made on a case-by-case basis, considering the severity of the reaction and the availability of alternative treatments 1.
In terms of prevention of future reactions, routine repeat penicillin skin testing is not indicated in patients with a history of penicillin allergy who have tolerated one or more courses of oral penicillin 1. However, consideration may be given to retesting individuals who have had prior penicillin anaphylaxis before repeating parenteral administration. The majority of delayed reactions to penicillin are mild and can be detected by single-day challenges, making multiple-day challenges unnecessary 1.
From the Research
Treatment of Penicillin Rash
- The treatment of penicillin rash depends on the type of reaction, which can be any of the 4 types of Gel-Coombs hypersensitivity reactions 2.
- Treatments include penicillin discontinuation, and depending on the type of reaction, epinephrine, antihistamines, and/or glucocorticoids may be used 2.
- For anaphylactic reactions, which can be life-threatening, acute management involves removal of the trigger, early administration of intramuscular epinephrine, and supportive care for the patient's airway, breathing, and circulation 3.
- Antihistamines, such as H1-antihistamines, can be used as adjunctive treatment therapy for acute anaphylaxis and anaphylactoid reactions, but they have a slow onset of action compared to epinephrine 4.
- In some cases, desensitization may be used to treat patients who require penicillin therapy 2.
Diagnosis and Evaluation
- Penicillin allergy can be evaluated using a penicillin allergy history algorithm (PAHA) and penicillin skin testing (PST) 5.
- The selection of the type of testing depends on the clinical setting, equipment availability, and type of hypersensitivity reaction 2.
- Patients with low-risk allergy histories may undergo direct amoxicillin challenge, while moderate-risk patients can be evaluated with penicillin skin testing 6.
- Penicillin skin testing carries a negative predictive value that exceeds 95% and approaches 100% when combined with amoxicillin challenge 6.
Management and Prevention
- Patients who have experienced an anaphylactic reaction should be monitored for a biphasic reaction, which can occur within 4 to 12 hours after the initial reaction 3.
- Management should focus on developing an emergency action plan, referral to an allergist, and patient education on avoidance of triggers and appropriate use of an epinephrine auto-injector 3.
- Antimicrobial stewardship is important to prevent the overuse of broad-spectrum antibiotics, which can increase the risk of antimicrobial resistance and adverse events 6.