What is the cause of a worsening rash, possibly due to strep (streptococcal infection) or an allergic reaction to amoxicillin, and how should it be managed with cetirizine (antihistamine) and hydrocortisone (corticosteroid) ointment?

From the Guidelines

The patient should discontinue the amoxicillin immediately and seek urgent medical attention within 24 hours for reassessment and documentation of the likely drug allergy. Given the widespread distribution of the rash and its worsening nature, this is likely an allergic reaction to the medication. For temporary relief, I recommend using over-the-counter diphenhydramine (Benadryl) 25-50mg every 6 hours as needed for itching, and applying over-the-counter 1% hydrocortisone cream to affected areas 2-3 times daily 1. The patient's symptoms do not currently indicate anaphylaxis, but any signs of breathing difficulties, facial swelling, or throat closure should prompt immediate emergency care. This reaction appears to be a delayed hypersensitivity reaction to amoxicillin, which commonly presents as a widespread rash 7-10 days after starting the medication, and can continue to worsen even after stopping the antibiotic 1. The patient should avoid penicillin-class antibiotics in the future unless cleared by an allergist. It is essential to note that the management of such reactions should prioritize the patient's safety and comfort, and the use of antihistamines like cetirizine, as initially prescribed, may be beneficial in alleviating symptoms, but the primary step is to discontinue the offending medication 1.

Some key points to consider in managing this patient include:

• The rash's widespread distribution and worsening nature suggest an allergic reaction to amoxicillin.
• Discontinuation of the antibiotic is the first step in management.
• Temporary relief can be achieved with over-the-counter diphenhydramine and hydrocortisone cream.
• Urgent medical attention is necessary for reassessment and documentation of the drug allergy.
• The patient should be educated on the signs of anaphylaxis and the importance of avoiding penicillin-class antibiotics in the future.

From the FDA Drug Label

1. 2 Severe Cutaneous Adverse Reactions Amoxicillin may cause severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP) If patients develop skin rash they should be monitored closely, and amoxicillin discontinued if lesions progress.

The patient is experiencing a worsening rash, which could be a sign of a severe cutaneous adverse reaction to amoxicillin.

• Discontinue amoxicillin: The patient should stop taking amoxicillin, as the rash may be a sign of an allergic reaction or other severe cutaneous adverse reaction.
• Monitor the patient closely: The patient should be closely monitored for any signs of worsening symptoms or progression of the rash.
• Alternative treatment: Consider alternative treatments for the patient's strep infection, if necessary. 2 2

From the Research

Patient's Condition

• The patient is experiencing a worsening rash, which is very red and spreading, despite being on day 9/10 of amoxicillin treatment for strep.
• The rash is located on the patient's legs, top and bottom of the feet, back, below the umbilicus, elbows, and arms.
• The patient denies any difficulty breathing, wheezing, or swallowing, and denies any swelling of the face, lips, or tongue.

Treatment

• The patient was prescribed cetirizine and hydrocortisone ointment today for the rash, but the medication could not be picked up.
• According to 3, cetirizine has been proven to be effective in the treatment of various forms of urticaria and reduces the pruritus of atopic eczema.
• Topical corticosteroids, such as hydrocortisone ointment, are an essential tool for treating inflammatory skin conditions, but their efficacy in acute irritant dermatitis is controversial 4.
• The combination of H1-antihistamines, such as cetirizine, and topical corticosteroids may have a synergistic effect in treating pruritus in atopic dermatitis 5.

Application and Dosage

• Topical corticosteroids can be applied once or twice per day for up to three weeks for super-high-potency corticosteroids or up to 12 weeks for high- or medium-potency corticosteroids 6.
• The quantity of corticosteroid prescribed depends on the duration of treatment, the frequency of application, the skin location, and the total surface area treated 6.
• Cetirizine is a safe second-generation antihistamine, and its dosage should be chosen based on the severity of symptoms, with doses higher than 10 mg (up to 40 mg) recommended for certain conditions 3.