Contact Dermatitis

Neomycin Allergy: Allergic Contact Dermatitis

Neomycin is an antibiotic used in topical ointments and creams for cuts and scrapes of the skin. Neomycin helps prevent bacteria from causing an infection in wounds. It works by blocking the cellular machinery that allows bacteria to live. Antibiotics only target the machinery of bacteria so that just bacteria die and not your own body’s cells. While a great over the counter antibiotic and widely used, you may also develop a contact dermatitis rash due to a neomycin allergy. Allergic contact dermatitis is an allergic reaction where you can get a rash days after coming into contact with an allergen.

Here is a classic story of someone who might have allergic contact dermatitis to neomycin:

John loves the outdoors. He’s always hiking, climbing, and riding bikes. He can get pretty scraped up sometimes and uses Bandaids and Neosporin to make sure his wounds heal up without infection. Recently though, the wound on his arm hasn’t been healing well. It’s been oozy and itchy, almost like he touched some poison ivy although he’s sure he didn’t. He’s worried the wound is infected.

In this case, we would be suspicious of John’s use of neomycin as a potential cause for this oozy wound. Real cases are usually much more complicated than these simplified stories, but they don’t have to be. If this story sounds similar to yours, it might be worth investigating if you have an allergic contact dermatitis to Neomycin.

What is it found in?

Neomycin is found in many over the counter medicines, ranging from first aid creams to eye drops to eardrops. For example, millions of Americans use products like Neosporin® or other triple antibiotic ointments for scrapes, cuts, and burns. Neomycin is commonly an active ingredient in these products.

Where will you be itching?

As with any contact allergen, itching and rashes occur at the site of contact. In this case, it will occur on wound that you apply neomycin too. It’ll look like an eczema patch or a poison ivy reaction.

The Benefits and Drawbacks of Topical Neomycin

Don’t get us wrong. Topical neomycin does have some benefits. A study showed that triple antibiotic ointments containing neomycin have been shown to reduce wound infection from 12.5% to 1.6%.  Another study showed that healing was promoted by 25%.

The drawback is that people can become allergic to neomycin.  In fact, it is a relatively common contact allergen.  The literature varies but a recent study showed that out of those that had allergy testing, 9% tested positive for a neomycin allergy.

You might be wondering why only topical neomycin is a problem. In short, your skin acts like a barrier.  When you have a wound or skin damage, your immune system tries to stop any foreign invaders like bacteria from entering your body. Repeated use of neomycin to a wound or scratch can eventually make your body recognize neomycin as just another invader.

What is the treatment for a neomycin allergy?

If this is happening to you when you apply neomycin, try avoiding topical products that contain neomycin.  This is the best way to prevent future skin irritation. Even if you are not experiencing symptoms yet, we suggest that if possible you choose OTC products that do not contain neomycin like Polysporin®. Studies suggest that repeated exposure to neomycin is what causes people to develop an allergic reaction to it over time.

Luckily, over the past few years, drug companies have started to use less neomycin in their products. However, since neomycin still is a commonly used ingredient, it is never a bad thing to read the label of products claiming “antibiotic” properties before buying them.

In addition, if you are allergic to neomycin, you might also be allergic to other antibiotics within the same class of antibiotics. Note that being allergic to neomycin does not automatically make you allergic to these other antibiotics! However, if you are still experiencing problems after eliminating neomycin, you might want to look into these other antibiotics as well.

Other Topical Antibiotics that May Cause a Rash Related to Neomycin

  • Gentamicin – Brand name: Garamycin®
  • Bacitracin – Brand Name: Baciguent ®, Polysporin®

Like neomycin, these topical antibiotics are used for preventing infections of minor wounds. Studies have shown that people are less likely to become sensitized to these topical antibiotics. However, it can happen and sometimes people that are allergic to neomycin are also allergic to these products. If your doctor recommends a topical antibiotic to put on a wound, we definitely recommend following your doctor’s orders. But, if you develop an itchy, red rash in the area then it may be  an allergic reaction to the topical antibiotic.

How is a neomycin allergy it diagnosed?

If you think neomycin is causing your rash, you can try avoiding the products we have listed above and see if the rash goes away. For example, in our cases above John could try using Polysporin instead of Neosporin when taking care of his wounds. If the rash comes back when you reuse the substance, then you may have found your culprit.

If you are unsure whether or not you have a neomycin allergy (contact allergens can be tricky!) you can talk to your dermatologist about patch testing. Patch testing is used to help doctors determine whether you have a true skin allergy (allergic contact dermatitis) or an irritant contact dermatitis (click here for the difference). This is determined by putting together your history, your job, your exposure, the environment, and your patch testing results.

Think a different contact allergen may be the culprit?

Check out our main list of common contact allergens.

References

Geronemus, R. G., Mertz, P. M., & Eaglstein, W. H. (1979). Wound healing: The effects of topical antimicrobial agents. Archives of dermatology, 115(11), 1311-1314.

Hood, R., Shermock, K. M., & Emerman, C. (2004). A prospective, randomized pilot evaluation of topical triple antibiotic versus mupirocin for the prevention of uncomplicated soft tissue wound infection. The American journal of emergency medicine, 22(1), 1-3.

Langford, J. H., Artemi, P., & Benrimoj, S. I. (1997). Topical antimicrobial prophylaxis in minor wounds. Annals of Pharmacotherapy, 31(5), 559-563.

Menezes de Pádua, C. A., Schnuch, A., Lessmann, H., Geier, J., Pfahlberg, A., & Uter, W. (2005). Contact allergy to neomycin sulfate: results of a multifactorial analysis. Pharmacoepidemiology and drug safety, 14(10), 725-733.

Schalock, PC. Common allergens in allergic contact dermatitis. In: UpToDate, Post TW(Ed), UpToDate, Waltham, MA. (Accessed on April 10, 2016.)