Penicillin and Other Drug Allergies: Signs and Causes

Drug allergy is a group of symptoms caused by an immune response to a medication. There may be no reaction on first use: the body only produces antibodies, and on repeated exposure they trigger the release of histamine and other substances. That is why allergy to medications develops only on repeated administration.

What drug allergy is and how it differs from a side effect

Drug allergy is a secondary reaction to a medication with general or local manifestations, based on an immune response involving B and T lymphocytes. Most adverse drug effects, however, are not associated with the formation of IgE antibodies: for example, aspirin can cause urticaria or trigger asthma without involvement of the immune system. Many people mistake an unpleasant but harmless side effect such as nausea for an allergy. Congenital defects of enzymes that inactivate a drug, as well as psychogenic reactions, are also separately confused with allergy.

Penicillin and related antibiotics allergy: how it manifests

Penicillin and related antibiotics are among the most common causes of drug allergy. Urticaria, itching of the skin or eyes, skin rash, swelling of the lips, tongue or face, and wheezing are typical. The only sign of a reaction is sometimes a prolonged fever, especially after administration of antibiotics. The reaction may occur immediately or hours after taking the drug, and in so-called serum sickness, a week or more later.

Reaction to ibuprofen, paracetamol, aspirin and other pain relievers

Aspirin is among the medications most often causing an allergic reaction.

Drug allergy in children

The symptoms of drug allergy in a child are the same as in adults: rash, urticaria, itching, swelling of the lips or face, wheezing. Drug allergy is a fairly rare phenomenon, so suspicion requires an assessment by a doctor rather than self-diagnosis.

How drug allergy is diagnosed

Examination may reveal low blood pressure, urticaria, rash, swelling of the lips, face or tongue, and wheezing. Skin tests help diagnose allergy to penicillin medications; there are no reliable skin or blood tests for other medications. If allergic-like symptoms have already occurred after taking a medication or a radiocontrast agent, the doctor often regards this as proof of allergy and does not order additional tests.

Danger signs and when to see a doctor

You should see a doctor if rash, itching, swelling or difficulty breathing appear while taking a medication. Severe reactions require treatment in a hospital, so delay is unacceptable.

On its own, it is not a reason to call an ambulance. 103 or 112 — if the lips, mouth, throat or tongue suddenly swell, breathing becomes very rapid or difficult, the throat tightens or swallowing is difficult, the skin, tongue or lips turn blue, pale or gray, the person suddenly becomes confused, drowsy or dizzy, loses consciousness and does not wake up, and the child becomes lethargic and does not respond as usual.

• Urticaria, rash and itching of the skin
• Swelling of the lips, tongue, face
• Wheezing
• Prolonged fever in response to an antibiotic

The material is for reference purposes and does not replace a doctor's consultation: only a specialist can assess the reaction and decide which examinations are needed.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer