Sunscreen is crucial protection for anyone spending time outside, but sometimes it doesn’t do the trick.

We got this email from a viewer.

Dear Dr. Manny,
I always apply sunscreen when I go outside, but still get sunburned. What am I doing wrong? Is the sunscreen not doing its job?
Thanks,
Grace

Research shows that sometimes sunscreen does not work as well if you have certain drugs, or food, in your body. These drugs can cause photo-toxic reactions, which increase sun sensitivity at high doses.

Acne treatments, antihistamines like Benadryl, and some forms of antibiotics are often linked to sun sensitivity.

Your skin could be extra vulnerable if you eat foods like celery and citrus fruits, particularly limes.

Try to avoid drinking alcohol while in the sun. Your body metabolizes alcohol into acetaldehyde, which makes the skin very sun sensitive. Plus, more alcohol means you might not remember to keep reapplying your lotion.

For more on how to avoid that sunburn, we checked in with an expert.

If you’re using sunscreen from last summer, it’s likely expired and not working properly, said Dr. Rebecca Kazin, of the Washington Institute of Dermatologic Laser Surgery in Washington, D.C.

“Not all sunscreen agents are the same. It’s important to look for ingredients including zinc, titanium, mexoryl or helioplex,” she said.

Give your sunscreen time to work— it’s optimal to apply it 20 to 30 minutes before you’re in the sun.

Finally, wear a broad-brimmed hat and swim shirt when you have fun in the sun, she added.

Do you have a health question? Email them to me at DrManny@foxnews.com.