A sulfa drug allergy generally describes an allergy to the class of drugs called sulfonamides. There are two types of sulfonamide drugs (Antibiotic and Nonantibiotic). The antibiotic type of sulfonamide is usually the one that causes sulfa drug allergy symptoms. Antibiotic sulfonamides include Bactrim® and SMZ-TMP (a generic name).
Sulfonamide antibiotics are often prescribed by a physician for treating urinary tract infections and ear infections (mainly in children). Due to the symptoms and the problems they may cause, physicians may be more inclined to prescribe penicillin when it seems appropriate. Sulfonamides, however, do not seem to produce an allergy any more frequently than other antibiotics do. This allergy is not influenced by the allergy season and can occur at any time.
Sulfa Drug Allergy Symptoms
Sulfa allergy symptoms tend to be progressive and can become life threatening if the sulfonamide is not discontinued. Some medications will produce adverse effects that diminish or disappear with continued treatment. This is not the case with sulfonamides; generally symptoms will continue to worsen until the sulfonamide is no longer being administered.
Allergy Symptoms by Body System Affected
- Skin - The most common symptom is a rash on the skin. This may continue to progress to a more severe swelling and pulling of body fluid to the skin’s layers. The fluid shift may cause an imbalance that can cause the circulatory system to fail (heart and blood vessels). Sulfonamide antibiotic treatment must be discontinued if a skin rash appears.
- Respiratory - Severe Sulfa allergic symptoms include lung collapse, allergy induced asthma and anaphylactic shock (the air passages close off and the person cannot breathe).
- Internal Damage – The liver or kidneys can be damaged and impaired.
Diagnosing an Allergy to Sulfa Drugs
Currently there is no sulfa drug allergy test and diagnosis is made by history of symptoms and physical examination. Treatment is aimed at preventing exposure to sulfonamides and other medications know to be similar to the chemical make-up or action of sulfonamides.
Similar drugs known to cause symptoms:
- Hydrochlorothiazide – A common diuretic (“water pill”), sometimes found in combination with a high blood pressure medication and given as one pill. Hydrochlorothiazide should not be given to patients with an allergy.
- Diabetic medications - Such as sulfonylureas (commonly dispensed as glipizide) are similar in composition as sulfonamides, but rarely do they produce allergic symptoms. A physician would need to monitor and weigh the options of giving these medications to a person with an allergy to sulfa drugs.
- Zonisamide - A medication for the treatment of seizures should not be taken by people with an allergy to sulfa drugs due to the skin reaction it may cause.
- Sulfasalasine - Another important medication for treating inflammatory bowel disease and arthritis should also not be used to treat sulfa drug allergy sufferers.
If you are ever on a sulfonamide or one of the above listed medications and develop a rash or shortness of breath, discontinue the medication and consult your health care provider. Be sure to alert medical professionals of your sulfa drug allergy or any other medication.
