Drug Rashes: 7 Medications That Can Cause Skin Reactions

Written by Rachel Feaster, PharmD, BCOP, BCPS | Reviewed by Maria Robinson, MD, MBA Published on March 1,

Key takeaways:

• Antibiotics, anti-seizure medications, and non-steroidal anti-inflammatory drugs (NSAIDs) can cause a variety of skin reactions. Warfarin, furosemide, and allopurinol can too.
• Skin reactions from medications range from mild rashes to severe, life-threatening conditions such as Stevens-Johnson syndrome and toxic epidermal necrolysis.
• Reach out to your healthcare team any time you develop a rash while taking medication. They can help you figure out next steps to prevent the rash from potentially turning into something more serious.

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Between multi-step skin routines, body scrubs, and face masks, we spend a lot of time caring for our skin. And rightly so — it’s our first line of defense against germs and it allows us to sense the world around us. Developing a skin reaction to something we consume or touch can then be particularly frustrating. Bumps, splotches, and itching are uncomfortable and often perceived as unattractive. 

Skin reactions have many causes, one of which is medications. But the types of skin reactions caused by medications are quite varied. They can range from a little redness to full-blown skin blistering. Below, we’ll discuss seven of the most common medications that can cause skin reactions and the types of rashes they cause.

What is a drug rash?

A drug rash is any skin breakout caused by a medication (including over-the-counter drugs and supplements). It’s usually caused by some type of allergic reaction, but it doesn’t have to be. A drug rash can develop immediately after starting a new medication, or it can take days or weeks.

Drug rashes cause changes in the color or texture of your skin, including things like: 

• Discoloration (like red or brown blotches)
• Bumps
• Peeling
• Blistering

Drug rashes are often itchy, but they can also be painful or have no sensation-related symptoms at all. 

Common types of drug rashes rashes

Medication-related rashes are grouped in many ways. But it’s easiest to classify them as either common and mild or rare and life-threatening. 

This isn’t a comprehensive list, but these are some of the more well-known and common reactions:

• Exanthematous (maculopapular) reactions. This type of rash typically starts as small bumps on the chest, stomach, or back and spreads to the arms and legs. In white skin, the bumps are red or pink. In darker skin, they can look purple, brown, or even skin-colored. It’s the most common type of rash, making up almost 90% of all drug reactions that involve the skin.
• Hives, angioedema, and anaphylaxis. Hives are itchy, raised patches on the skin. Angioedema is related to hives, but the swelling happens under the skin. Both of these conditions can evolve to a more life-threatening reaction called anaphylaxis. These reactions are the second most common type of drug rash.
• Fixed drug eruption. This usually appears as a single round red, violet, or brown skin patch. Occasionally, there are several patches, and sometimes they can blister. It’s called “fixed” because if the reaction recurs upon restarting the same medication after stopping it, it will appear on the same spot on your body as before.
• Drug-induced vasculitis. This rash is caused by blood vessel inflammation. The inflammation allows blood to leak into the skin. The resulting rash looks like tiny purple or brown spots that can turn into bumps or blisters.

Less common drug rashes

Other medication-related rashes are more rare, but they can be life-threatening. They represent about 2% of medication-related skin rashes.

• Erythroderma. This is an intense rash that causes skin redness on more than 90% of the body. It can progress to more serious problems, like peeling, swelling, and loss of body temperature regulation. 
• Drug rash with eosinophilia and systemic symptoms (DRESS). This reaction typically starts as itchy patches or bumps that can appear red (in white skin) or brown/purple (in darker skin). It can also come with body-wide symptoms, such as swelling and fever, and cause damage to organs like the liver.
• Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). These two related conditions commonly start with flat, dark red, purple, or brown patches that can be painful. These can rapidly progress to skin peeling, and painful sores in the mouth, eyes, or genitals. Other symptoms include flu-like symptoms, such as fever and body aches. They’re different only in how much of the skin they affect — SJS affects less than 10% of your body, whereas TEN affects 30% or more.
• Acute generalized exanthematous pustulosis (AGEP). This rapidly spreading rash looks like small, pimple-like white heads. It becomes life-threatening when organs like the liver, kidney, or lymph nodes get involved.
• Serum sickness-like reaction. This rash can have many different appearances, including red or violet bumps, hives, or tiny purple or brown spots. The other symptoms that make it a serum sickness-like reaction include joint aches, fever, and itching. While this condition is rare, it’s typically not life-threatening.

Now, let’s look at the various types of medications that could cause these skin reactions.

1. Antibiotics like Bactrim

Antibiotics are notorious for a risk of causing skin rashes and allergic reactions. Sulfa and penicillin antibiotics are common culprits.

Bactrim (sulfamethoxazole/trimethoprim) is part of a group of medications called sulfonamides. People with “sulfa” allergies are allergic to these types of medications. It can also cause a range of skin reactions — the most common being an exanthematous rash. It typically happens 1 to 2 weeks after starting Bactrim and resolves soon after stopping it. Bactrim has also been linked to skin reactions like SJS/TEN, DRESS, and AGEP.

Keflex (cephalexin) is a cephalosporin antibiotic. Compared to other medications in the same class, it has the highest risk of causing a skin reaction. Like Bactrim, it’s been connected to a few possible reactions, including exanthematous rash, hives, and serum sickness. 

Penicillin is related to medications like Keflex. They have the same basic chemical structure. This means that if you have a serious reaction to Keflex (or another cephalosporin), you shouldn’t take penicillin. Skin reactions to penicillin range from mild to serious.

Other antibiotics can also cause sensitivity to the sun.

2. Hydralazine

Hydralazine is a blood pressure medication that can cause drug-induced lupus erythematosus (DILE). This is the same as the autoimmune condition systemic lupus erythematosus. It can cause several different rashes, including a red butterfly-shaped rash across the nose and cheeks and other sun-exposed skin. DILE can also lead to joint aches, fever, and organ inflammation. 

Another well-known cause of DILE is a heart medication called procainamide. 

3. NSAIDs like aspirin

Aspirin is a pain and fever reducer. It’s a type of nonsteroidal anti-inflammatory drug (NSAID), alongside medications like ibuprofen (Advil, Motrin) and naproxen (Aleve).

Skin reactions to these medications are rare, but possible. They can range anywhere from mild hives to angioedema and anaphylaxis. Reported reactions happening at least 24 hours after taking an NSAID include exanthematous rashes, fixed drug eruptions, and severe reactions like DRESS and AGEP.

If you have a reaction to aspirin, it’s likely that you’ll have a reaction to other NSAIDs, too.

4. Furosemide

Furosemide (Lasix) is a diuretic, commonly known as a “water pill”. Like Bactrim, it’s part of the sulfonamide family. So if you have an allergy to sulfa antibiotics, it’s possible you could react to furosemide too.

Reported skin reactions to furosemide include rash, itching, and hives. More rare and severe reactions have included DRESS, SJS/TEN, and erythroderma. 

5. Anti-seizure medications like carbamazepine

Anti-seizure medications cause rash and hypersensitivity reactions in up to 9% of people who take them. The most common medications to cause rash include carbamazepine (Tegretol), oxcarbazepine (Trileptal), phenytoin (Dilantin), and lamotrigine (Lamictal).

Mild exanthematous rashes are the most common. The risk of these rashes can be minimized by avoiding high starting doses and increasing your dose slowly over time. 

Anti-seizure medications are also associated with DRESS and SJS/TEN. Carbamazepine has a boxed warning for SJS/TEN in people with a specific genetic mutation (HLA-B*1502). There is a strong connection between having this mutation and developing SJS/TEN. This mutation is more common in people of Asian ancestry, so screening in this group before starting carbamazepine is recommended.

6. Warfarin

Warfarin (Coumadin, Jantoven) is a blood thinner that treats and prevents blood clots. Unusual or enlarged bruises can occur if your dose is too high. If this happens, you should call your healthcare provider immediately. They will likely want to do a quick blood draw to test your INR, which tells them how much your blood is clotting.

Another rare but serious side effect is warfarin-induced skin necrosis. These are red, violet, or brown plaques that can develop into blisters, ulcers, and skin death (necrosis). The risk is higher in those with certain genetic conditions that have a higher risk for blood clots.

7. Allopurinol

Allopurinol (Zyloprim) is a medication used for decreasing high uric acid levels, most commonly in cancer and gout. The most common side effect that it causes is an itchy flat or bumpy rash. This can sometimes progress to severe conditions like DRESS or SJS/TEN. 

The risk for developing a more serious skin condition is higher when you’re first starting allopurinol. It’s also higher in people with impaired kidney health, starting at a high dose, and in those with a genetic mutation called HLA-B*58:01.

As a precaution, contact your healthcare provider right away if you develop a rash while taking allopurinol.

What should you do if you’re having a skin reaction to a medication?

It’s easy to ignore a rash and hope it goes away on its own. But rashes can progress to more serious conditions if left untreated. 

If you develop a rash after starting a new medication, contact your provider to discuss your symptoms and see if you should continue taking the medication. If you have a rash, plus any of the following symptoms, it could mean a more serious rash and you should seek immediate medical attention:

• Blistering or peeling (on skin or lining of mouth, nose, or genitals)
• Fever
• Open sores
• Pain
• Shortness of breath
• Swelling of the face or throat
• A fast-spreading rash

The bottom line

The most common medications that cause skin reactions are antibiotics, anti-seizure medications, and NSAIDs. There are also well-known individual medications that cause more unique rashes, such as hydralazine, warfarin, and allopurinol.