Sulfasalazine can cause hair loss, but it’s classified as a rare side effect. The FDA’s prescribing information for Azulfidine (the brand name for sulfasalazine) lists alopecia under “less common or rare adverse reactions.” So while it does happen, most people taking this medication won’t experience noticeable hair thinning or shedding.
That said, if you’re on sulfasalazine and finding more hair in your brush or shower drain, the connection is worth understanding. The drug’s effect on a specific nutrient plays a central role, and there are practical steps that can help.
How Sulfasalazine Affects Hair Growth
Sulfasalazine interferes with your body’s ability to absorb and use folate (vitamin B9), a nutrient that’s essential for cell division, including the rapidly dividing cells in hair follicles. Research published in The Journal of Clinical Investigation found that sulfasalazine acts as a competitive inhibitor of intestinal folate transport, essentially blocking the pathway your gut uses to absorb folate from food. The drug also inhibits several enzymes that process folate once it’s inside the body, all at clinically relevant concentrations.
The researchers described sulfasalazine as having “certain properties of an antifolate drug.” That’s significant because folate deficiency is a well-established cause of hair loss. When your hair follicles don’t get enough folate, they can’t produce new cells efficiently, which may push more hairs into the resting phase of the growth cycle. The result is diffuse thinning or increased shedding rather than patchy bald spots.
Your Underlying Condition May Also Play a Role
Sulfasalazine is commonly prescribed for inflammatory bowel disease (IBD), rheumatoid arthritis, and other autoimmune conditions. These conditions themselves can trigger hair loss independently of any medication. A study examining hair loss in IBD patients identified several overlapping causes: the autoimmune process itself, nutritional deficiencies from malabsorption, telogen effluvium triggered by chronic inflammation or stress, and medication side effects.
This overlap makes it tricky to pinpoint whether your hair loss is from sulfasalazine, from the disease it’s treating, or from both. A few patterns can help you sort it out:
- Timing matters. If hair loss started within a few weeks to a few months of beginning sulfasalazine (or increasing the dose), the medication is more likely involved. Drug-induced hair loss typically follows a delay of two to four months because of how long it takes for hair follicles to shift into their resting phase.
- Pattern of loss. Medication-related hair loss tends to be diffuse, meaning it thins evenly across your scalp. If you’re seeing distinct patches, that’s more suggestive of alopecia areata, which is an autoimmune process that can coexist with the conditions sulfasalazine treats.
- Disease activity. If your underlying condition is flaring at the same time, the inflammation and physical stress of a flare can independently cause telogen effluvium, a type of temporary shedding.
Folate Supplementation as Prevention
Because sulfasalazine’s effect on hair is largely driven by folate depletion, supplementation is the most straightforward countermeasure. A daily folic acid supplement of 1 mg is recommended for all patients on prolonged sulfasalazine therapy. This isn’t specific to hair loss prevention; it’s standard guidance to offset the drug’s antifolate properties and protect against a range of folate-deficiency symptoms, including anemia, fatigue, and mouth sores.
If you’ve been taking sulfasalazine without a folic acid supplement and are now noticing hair changes, starting supplementation may help over time. Hair growth is slow, so you likely won’t see improvement for several months. The shedding needs to stop first, and then new growth needs time to come in. Most people notice a difference within three to six months of correcting a folate deficiency.
What to Do If You’re Losing Hair on Sulfasalazine
First, check whether you’re already taking folic acid. If not, that’s the easiest intervention. If you are and you’re still losing hair, it’s worth having your folate and iron levels tested, since both nutrients are commonly depleted in people with IBD or chronic inflammatory conditions, and both affect hair growth.
Some people find that the hair loss resolves on its own even without stopping the medication, particularly once the body adjusts or supplementation catches up. In cases where shedding is significant and clearly linked to the drug, switching to a different medication in the same class may be an option your doctor considers. Sulfasalazine is one of several disease-modifying drugs used for conditions like rheumatoid arthritis, so alternatives exist.
It’s also worth noting that drug-induced hair loss from sulfasalazine is not permanent. The follicles aren’t damaged; they’re simply not getting the nutrients they need for active growth. Once the cause is addressed, whether through supplementation, dose adjustment, or switching medications, hair typically regrows fully.