SULFA ALLERGY

I am suffering a rash caused by sulfa allergy now. This is the first time that I got the allergenic reaction triggered by sulfonamides. All of a sudden, I got the sulfa allergy and it has never happened in the past 20 years. I think this might be the birthday gift to me given by so-called God... Thus, I collect some information about sulfa allergy which also based my own experience and knowledge.  

-What is sulfa allergy?

"Sulfa allergy" is a term used to describe adverse drug reactions to sulfonamides. It is well-known for students who have had biological classes in China that antibiotic sulfonamides were the first antibiotics used to treat infections. However, they are less likely to be used because of their common side effects.

My allergy was caused by Trimethoprim-sulfamethoxazole (or Septra, Bactrim) given by a doctor of UHS to treat my skin’s infection. I would rather try my own “prescription” next time because I know exactly what kind of medicine I should use but it is really a pity that most antibiotic medicine cannot be bought without medical prescription in America. Although sulfonamides are the trigger of allergy, not all drugs which contained them could cause allergy. The difference is that it has antibiotic characteristics or not. The antibiotic sulfonamides are different structurally from the non-antibiotic sulfonamides, and appear to be much more likely to result in allergic reactions. Many of the sulfa non-antibiotics do not cause problems in people with sulfa antibiotic allergy.

-How common is sulfa allergy?

The overall incidence of adverse drug reactions to sulfa antibiotics is approximately 3%, similar to other common antibiotics such as penicillin. Certain groups of people have a higher risk for it, including those with immune problems such as AIDS.

-What symptoms are common in sulfa allergy?

~Skin reactions. 

Skin reactions are the most common adverse reactions to sulfa medications, ranging from various benign rashes to life-threatening Stevens-Johnson syndrome and toxic epidermal necrolysis.  

Hives and increased photosensitivity are also possible. There is a possibility that if the sulfa medication is continued despite a mild rash occurring, the rash could progress to a more severe form of skin reaction.

I have to wear long-sleeve clothes and hat no matter how hot the day is nowadays because I am really sensitive to sunlight. Here are two pictures of my arm and hand.

~Liver and kidney injury.

People with sulfa allergy may also develop a type of hepatitis, and kidney failures.

~Lung reactions. 

Sulfa allergy can also affect the lung with pneumonia-like reactions, which could worse asthma and vasculitis.

~Blood reactions. 

Sulfa allergy can also affect various blood cells, resulting in decreased white blood cells, red blood cells, and platelets.

-How is sulfa allergy diagnosed?

Unlike penicillin, there is no skin test or blood test available to diagnose sulfa allergy. Therefore, the diagnosis is made when a person, who is taking a sulfonamide medication, experiences symptoms consistent with those seen mentioned above in sulfa allergy. In my case, I got the rash after taking 3 pieces of Bactrim and it was getting worse after two more pieces. Actually, the only method of determining whether it is sulfa allergy or not is taking more medicine containing sulfonamides and watching if the symptom worsens. If it gets worse, it is sulfa allergy.

-How is sulfa allergy treated?

In most cases, if a person is experiencing an adverse reaction to a sulfa medication, that medication should be stopped at first. The symptoms of the reaction need to be treated as soon as possible especially in those experiencing Stevens-Johnson syndrome or toxic epidermal necrolysis. Antianaphylaxis are necessary for treating allergy reactions. Prednisone is a common used medicine works on immune system. Banophen (diphenhydramine) is a kind of antihistamine, which used for temporary relief from symptoms of upper respiratory allergies, hay fever, sneezing, runny nose, itchy, etc, most of these are allergy reactions. One of the side effects of the latter is drowsiness, which caused lots of troubles to me.

-What medications should sulfa-allergic patients avoid?

~Sulfa antibiotics. 

Trimethoprim-sulfamethoxazole (Septra, Bactrim and generics), sulfadizine, sulfisoxazole, and dapsone.

 Sulfacetamide eye drops/shampoos/creams, silver sulfadiazine cream, and sulfanilamide vaginal preparations.

~Diuretics (water pills). 

The risk for sulfa-containing diuretic medications causing reactions in sulfa-allergic patients is low. Many diuretic medications, such as hydrochlorothiazide (HCTZ) and furosemide (Lasix) are sulfa-based, while ethacrynic acid (Edecrin) is not.

~Sulfonylureas. 

Oral medications used for the treatment of diabetes, called sulfonylureas (such as chloropropamide, glyburide, and glipizide), are structurally similar to sulfonamides. Although there are a few reports of these medications causing problems in sulfa-allergic patients, they should take care when taking these medications.

~Sulfasalazine. 

Sulfasalazine is a sulfonamide that is related to aspirin, and is used for inflammatory bowel disease and rheumatoid arthritis.

~Zonisamide. 

Zonisamide is a sulfonamide medication used for the treatment of seizures. It has been associated with severe skin reactions, which are typically sulfa allergenic reactions.