On a sunny spring day, enjoying the scenery is a great idea, but it's important to be mindful of the medication you're taking. Some medications can increase your sensitivity to the sun, causing photosensitivity reactions. Whether you're taking oral or topical medication, it can be absorbed into your body and end up on your skin, leading to symptoms when exposed to sunlight.

If you're taking medication, it's essential to limit your time outdoors on days with high UV levels. To determine the UV index for the day, you can easily search for "today's UV index" online. It's especially important for individuals taking antibiotics, diuretics, cholesterol-lowering drugs, anti-inflammatories, and dermatologic medications to avoid direct sun exposure as much as possible.

Limit your direct sun exposure from 10 a.m. to 4 p.m. when the sun's rays are the strongest. Take shade breaks whenever possible during outdoor activities. Wearing a wide-brimmed hat, sunglasses, a parasol, long-sleeved shirts, and long pants can all help to some extent in protecting your skin from the sun. If your clothes get wet, they offer little protection. None of these methods will protect you from all UV rays. You should still wear sunscreen whenever you go outside, but you should be extra careful and thorough when you're on medication.

Which sunscreen should we use? There are two types of UV rays -- UVA and UVB. UVA rays are mainly responsible for skin aging, while UVB rays cause sunburn. Medication-induced photosensitivity reactions can be caused by both. The risk of sunburn from UVB is even higher during medication use. Therefore, it is best to use a sunscreen that protects against both UVA and UVB rays.

it comes to applying sunscreen, it's crucial to apply enough and often. It's better to err on the side of applying too much rather than too little. Sunscreen that physically blocks light is effective as soon as you apply it. But chemical sunscreens, which work by absorbing UV rays and converting them into heat energy, need time to build up a protective layer on your skin. It's best to apply sunscreen 15 to 30 minutes before going outside. As a general rule, you should reapply every two hours, but if you sweat a lot, you may need to reapply more often.

Not all medications cause photosensitivity. However, hundreds of medications have been linked to photosensitivity, so it's important to be cautious. While most sunscreens on the Korean market have been proven to be safe, there are rare cases where the sunscreen itself can cause photosensitivity. It's best to consult with your pharmacist to make sure your medication doesn't require sunscreen.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness and medications. This column was originally published in Korean in Joongang Ilbo on April 13, 2023. – Ed.