From the Guidelines
Amoxicillin can cause a skin rash, with most reactions being mild and occurring within a few days to two weeks after starting the medication. According to a 2022 practice parameter update on drug allergy published in the Journal of Allergy and Clinical Immunology 1, delayed reactions to penicillins, including amoxicillin, can occur in 5%-12% of subjects, with most reactions being self-reported and mild. The study suggests that single-day challenges can detect the majority of delayed reactions, and multiple-day challenges are not recommended after negative single-day challenges.
Some key points to consider:
- The rash typically appears as small, pink to red spots that may be flat or slightly raised, often starting on the trunk and spreading outward.
- Most amoxicillin-related rashes are mild and not dangerous, representing a non-allergic reaction.
- However, some rashes can indicate a true allergic reaction, especially if accompanied by symptoms like facial swelling, difficulty breathing, or severe itching.
- If you develop a rash while taking amoxicillin, contact your healthcare provider, but don't stop taking the medication unless instructed to do so.
- The rash may resolve on its own even while continuing the antibiotic, as suggested by the study 1.
It's essential to note that amoxicillin rashes are more common in patients with certain viral infections, particularly Epstein-Barr virus (mononucleosis), where up to 90% of patients may develop a rash when given amoxicillin, although this specific information is not mentioned in the study 1.
From the FDA Drug Label
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. A high percentage of patients with mononucleosis who receive amoxicillin develop an erythematous skin rash. The most common adverse reactions (greater than 1%) observed in clinical trials of amoxicillin for oral suspension were diarrhea, rash, vomiting, and nausea.
Amoxicillin can cause a skin rash. Patients who develop a skin rash should be monitored closely, and amoxicillin should be discontinued if lesions progress 2. Additionally, patients with mononucleosis are at a higher risk of developing a skin rash when taking amoxicillin 2.
From the Research
Amoxicillin and Skin Rash
- Amoxicillin can cause a skin rash in some patients, with studies suggesting that it is one of the antibiotics that can induce adverse reactions 3, 4, 5, 6.
- The skin rash can be a maculopapular rash, which is a benign, nonallergic phenomenon, or it can be a more severe reaction such as Drug Rash Eosinophilia and Systemic Symptoms (DRESS) syndrome 7, 4, 5.
- DRESS syndrome is a severe cutaneous drug reaction characterized by a skin rash, eosinophilia, atypical lymphocytosis, and involvement of multiple organs, and amoxicillin has been well-documented as a potential cause of this syndrome 4, 5.
- The incidence of antibiotic-induced skin rash in patients with infectious mononucleosis may be higher than in the general population, with amoxicillin being one of the top reported drugs associated with this adverse effect 6.
Types of Skin Reactions
- Maculopapular rash: a benign, nonallergic phenomenon that resolves spontaneously in a few days without sequelae 7.
- Urticaria: a type of skin reaction that can occur in about one third of cases 7.
- DRESS syndrome: a severe cutaneous drug reaction characterized by a skin rash, eosinophilia, atypical lymphocytosis, and involvement of multiple organs 4, 5.
- Vasculitic rash: a rare adverse effect of amoxicillin 3.
Patient Populations at Risk
- Patients with a viral illness, infectious mononucleosis, and lymphocytic leukemia may be at a higher risk of developing a skin reaction to amoxicillin 7, 6.
- Patients who are taking certain medications, such as sulfasalazine, may be at a higher risk of developing DRESS syndrome when taking amoxicillin 4, 5.