Despite having similar names and symptoms, sulfa and sulfite allergies are different. Sulfa refers to sulfonamides, known as sulfa drugs, while sulfite is commonly found in wine, processed food, and condiments.

Sulfites and sulfa medications are chemically unrelated, but because their names are similar, people often confuse one with the other.

Sulfa drugs were the first successful treatment against bacterial infections in the 1930s. They’re still used today in antibiotics and other medications, like diuretics and anticonvulsants. People with HIV are at particular risk for sulfa sensitivity.

Sulfites occur naturally in most wines. They’re also used as a preservative in other foods.

Symptoms of an allergic reaction to sulfa include:

  • hives
  • swelling of the face, mouth, tongue, and throat
  • drop in blood pressure
  • anaphylaxis (a severe, life threatening reaction that requires immediate medical attention)

Rarely, cases of serum sickness-like reactions can occur around 10 days after a sulfa drug treatment begins. Symptoms include:

  • fever
  • skin eruptions
  • hives
  • drug-induced arthritis
  • swollen lymph nodes

You should contact a doctor immediately if you have these symptoms.

Medications to avoid

Avoid the following medications if you’re allergic or have a sensitivity to sulfa:

Safe medications for people with sulfa allergies

Not all drugs that contain sulfonamides cause reactions in all people. Many people with sulfa allergies and sensitivities may be able to safely take the following medications but should do so with caution:

The ability to take these medications can vary from person to person. If you have a sulfa allergy and are unsure if you should take any of these medications, talk with your doctor.

Symptoms of an allergic reaction to sulfites include:

  • headache
  • rash
  • hives
  • swelling of the mouth and lips
  • wheezing or trouble breathing
  • asthma attack (in people with asthma)
  • anaphylaxis

If you experience more serious symptoms of a sulfite allergy, contact your doctor. Anaphylaxis requires emergency medical attention.

According to the Cleveland Clinic, people with asthma have between a 1 in 20 and 1 in 100 chance of having a reaction to sulfites.

Sulfites are common in processed foods, condiments, and alcoholic beverages, such as red and white wine. Sulfites occur naturally in wine during fermentation, and many winemakers add them to help the process along.

For the past two decades, the Food and Drug Administration (FDA) has required winemakers to display the warning “contains sulfites” if levels exceed a certain threshold. Many companies voluntarily add the label to their products as well.

If you have sensitivities, you should avoid food products with the following chemicals on the label:

  • sulfur dioxide
  • potassium bisulfate
  • potassium metabisulfite
  • sodium bisulfite
  • sodium metabisulfite
  • sodium sulfite

Work with your doctor to determine the best course of action if you suspect you have a sulfa or sulfite allergy. You may need to see a specialist or undergo further testing. Be sure to talk to your doctor about which medications and products to avoid, especially if you have asthma.