Introduction to Trimethoprim and Sun Exposure

As someone who enjoys spending time outdoors, I always make sure to take precautions when it comes to sun exposure. That's why I was surprised to learn that certain medications, like the antibiotic trimethoprim, can actually increase your sensitivity to the sun. In this article, I will discuss everything you need to know about trimethoprim and sun exposure, from the reasons behind this increased sensitivity to the best ways to protect yourself.

Understanding Trimethoprim and Its Uses

Before we dive into the relationship between trimethoprim and sun exposure, it's important to understand what trimethoprim is and why it might be prescribed to you. Trimethoprim is an antibiotic that is commonly used to treat bacterial infections, such as urinary tract infections (UTIs), respiratory infections, and ear infections. It works by inhibiting the growth of bacteria, allowing your immune system to effectively fight off the infection.


Trimethoprim is often prescribed in combination with another antibiotic called sulfamethoxazole. Together, these two medications form a powerful antibiotic known as co-trimoxazole or Bactrim. This combination is particularly effective against a wide range of bacteria, making it a popular choice for treating various infections.

Increased Sun Sensitivity: The Link Between Trimethoprim and Sun Exposure

Now that we know what trimethoprim is and what it's used for, let's discuss the connection between this medication and sun exposure. Trimethoprim, especially when combined with sulfamethoxazole, can cause increased sensitivity to the sun. This is because these antibiotics can make your skin more susceptible to the harmful effects of ultraviolet (UV) radiation.


This increased sun sensitivity, also known as photosensitivity, can result in a higher risk of sunburn and skin damage, even after just a short amount of time in the sun. In some cases, people taking trimethoprim may also develop a rash or experience increased skin redness when exposed to sunlight.

Protecting Your Skin: Tips for Staying Safe in the Sun While Taking Trimethoprim

If you're taking trimethoprim, it's crucial to take extra precautions to protect your skin from the sun. Here are some tips for staying safe while enjoying the outdoors:

  1. Wear sunscreen: Apply a broad-spectrum sunscreen with an SPF of at least 30 to all exposed skin, and make sure to reapply every two hours, or after swimming or sweating.
  2. Seek shade: Whenever possible, seek shade during peak sun hours (usually between 10 a.m. and 4 p.m.). This can help minimize your exposure to harmful UV rays.
  3. Wear protective clothing: Long sleeves, pants, and wide-brimmed hats can provide additional protection from the sun. Look for clothing with a UPF (ultraviolet protection factor) rating for added sun protection.
  4. Wear sunglasses: Protect your eyes from UV rays by wearing sunglasses that block 100% of UVA and UVB radiation.
  5. Stay hydrated: Sun exposure can be dehydrating, so make sure to drink plenty of water throughout the day to stay hydrated and help your body regulate its temperature.
  6. Be cautious with tanning: While it might be tempting to get a tan, it's important to remember that tanning can increase your risk of skin damage and skin cancer. Opt for self-tanning products instead of tanning beds or sunbathing.

When to Talk to Your Doctor About Trimethoprim and Sun Exposure

If you're taking trimethoprim and are concerned about sun exposure, it's important to discuss your concerns with your healthcare provider. They can help you determine the best course of action for protecting your skin and may be able to recommend alternative medications if needed. It's also crucial to contact your doctor if you experience any severe sunburn, rash, or other skin reactions while taking trimethoprim, as these could be signs of an adverse reaction to the medication.

Conclusion: Staying Safe in the Sun While Taking Trimethoprim

In conclusion, it's essential to be aware of the increased sun sensitivity that can occur when taking trimethoprim. By following the tips provided in this article and discussing any concerns with your healthcare provider, you can help protect your skin from the harmful effects of the sun while still enjoying your time outdoors. Remember, it's always better to be safe than sorry when it comes to sun exposure and the health of your skin.