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Updated: Aug 26, 2022

I am asked on a regular basis about patients being allergic to sulfa drugs and if they can have local anesthetic since it has sulfites in it. The quick answer is yes you can, because even though they sound the same they are different.

With all the different “sulf” prefix medications out there it can be confusing how to handle situations with your patients. It’s enough to make you want to “sulfocate” …ok. That was a super cheesy joke, but I really couldn't help myself.

Here is a little review of the top three “sulf” items used in dentistry. They are sulfa, sulfate and sulfite.


Sulfas are part of what I will call the medication family. These are mainly known as antibiotics but are also found in other medications too. What I found interesting is learning that several medications our patients take fall into the sulfa drug category. For example, glyburide (diabetes), Azulfidine (Crohn’s, rheumatoid arthritis), Imitrex (migraines), as well as several medications which fall into the diuretic’s classification. The anti-inflammatory drug Celebrex is also a sulfa drug. It’s not often a dental professional would recommend an anti-inflammatory medication, but just in case, it’s a good idea to double check that your patient is not allergic to sulfas. Thankfully, the allergy rate is rather rare, only 3-8% of people have a sulfa allergy.

Remember Sulfa is the Drug.


Sulfites are part of the preservative family. These are often found in food and drugs to increase shelf life and reduce oxidation. You may have first learned about sulfites as being used to preserve food at a buffet line. My understanding is this hasn’t been used for nearly 3 decades. One popular way of identifying a sulfite sensitivity is if your patient says they can’t drink wine because of the sulfites. However, not everyone can test their sulfite reaction when drinking wine. Other foods which have been known to have sulfites are shrimp (fresh or frozen), bottled lemon/lime juice, some canned vegetables, tea, and several condiments.

In dentistry, we are most concerned about sulfites because it is a preservative in anesthetics having a vasoconstrictor. If the anesthetic didn’t have this preservative, then the vasoconstrictor would lose its effectiveness before it made it from the manufacturer to the syringe.

For the general population sulfite allergy is rare. However, with those who have asthma, there is an increase in sensitivity. Approximately 5-10% of patients with asthma could have an adverse reaction to sulfite drugs. What’s ironic is a sulfite allergic reaction usually shows up as bronchospasm. Some food for thought, if you have a patient with active asthma, with no known sulfite allergy, it may be a good idea to have their medication on hand if you must use local anesthetic with vasoconstrictor. Better yet, try to avoid vaso’s all together.

Remember Sulfite is for Shelf Life.


Sulfates are in the mineral family. This is a mineral salt found in soil and water along with household items like detergents, for example toothpaste, in the form of sodium lauryl sulfate (SLS). The purpose of SLS is twofold. It’s acts as a surfactant or bonding agent for the oil and water-based ingredients. When oil and water are combined it makes the cleaning aspect of the detergents more effective. SLS also creates the foaming action we’ve all come accustomed to when we think of something getting clean. Allergic reaction is rare. The most common reaction is tissue sloughing and dry lips. This is one reason our patients may request toothpastes that are SLS free.

Remember Sulfate keep it Clean Mate.

Next time you have a patient who says they have a sulfa allergy, please remember local anesthetics with vasoconstrictors have sulfites. They are different drugs and affect our patients differently. And as always, talk with your patient. Get to know their health history. Ask them questions about their medications and reactions to different foods. My hope is this will help clarify some questions about the difference between all the “sulf” items out there.

Here is a little poem to help keep them straight

Go out there and hit it your best shot!



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