About Allergic Reactions to Amoxicillin

Amoxicillin is one of the drugs in the beta-lactam antibiotic family, according to the Mayo Clinic. It is used to treat bacterial infections. Because it is inexpensive compared to other antibiotics, it is regularly prescribed to treat common conditions such as strep throat, middle ear infections, dental tissue infections, gonorrhea, and upper and lower respiratory tract infections.

Developing Amoxicillin Allergies

The Mayo Clinic states that allergy to amoxicillin is not genetic, but acquired by persons exposed to the drug at some point in medical treatment. Individuals allergic to the penicillin family are not certain to have an allergic reaction to amoxicillin. Women, people with HIV/AIDS and cystic fibrosis patients have a higher risk for an allergic reaction to the drug, according to the Mayo Clinic staff.

Mild Allergic Reactions

Medical researchers at Carlos Haya Hosptial in Malaga, Spain, have reported that delayed hypersensitivity reactions to amoxicillin and other drugs in the penicillin family are rare. Allergic reactions may begin in a mild form, such as a rash, and progress to more severe reactions. According to the Centers for Disease Control and Prevention (CDC), common allergic reactions to amoxicillin include stomach upset (including vomiting) and diarrhea.

Severe Allergic Reactions

Allergic rashes may occur on any part of the body, but a rash typically develops first on the chest, arms or legs. The rash may or may not itch. The CDC reports that swelling is another common allergic reaction, and that it may occur on the tongue and threaten to impede airways. The hands and feet may also swell. These reactions may or may not be accompanied by a fever. Anaphylactic reactions are the most severe allergic response, involving heart arrhythmia and difficulty in breathing. This allergic response may be immediate or may develop during the course of treatment. Immediate medical intervention is necessary in anaphylactic reactions.

Skin Testing

Because amoxicillin is effective in treating bacterial infections and the cost is lower than many other antibiotics, doctors may test a patient with known penicillin allergy to determine if amoxicillin may be prescribed. This test requires the patient to be injected with small amounts of the drug under the skin to determine the severity of a potential allergy. The arm or back is usually used for testing because the reaction can be immediately assessed in these areas. If a swelling or a red rash develops around the injection site, amoxicillin is not to be prescribed. If the injection site has little reaction, the doctor may decide to prescribe the drug. The Mayo Clinic recommends doctors take a medical history, with a detailed explanation of past penicillin drug reactions, prior to the skin test.

Treatment for Allergic Reactions

Doctors will halt treatment with amoxicillin when an allergic response takes place. According to the Mayo Clinic, mild reactions such as hives and rashes are treated with over-the-counter medicines including Benadryl. Severe rashes are treated with an oral course of cortiscosteroids. In extreme cases, some doctors may inject corticosteroids. Treatment for the most severe allergic reaction, anaphylaxis, requires an emergency room visit with epinephrine injections as well as blood pressure and breathing monitoring. Some patients require emergency treatment as well as injections to reduce allergic hives.