Summer is finally here, which also means it’s the official start of sunblock season.

Applying sunblock may seem easy enough, but in reality there are a number of factors that determine just how effective (or ineffective) your sunscreen may actually be. Here’s what the experts have to say about applying sunblock this summer to ensure that neither you nor your loved ones catches a burn.

Not Using Enough

What’s the point in wearing the highest factor of sunblock if you’re not wearing enough to actually get the job done? Dr. Sonam Yadav, a dermatologist and medical director at the Juverne Skin Care Center in New Delhi told Medical Daily that she advices consumers to use at least one teaspoon of sunblock on the face and one shot glass for the body.

In addition, Yadav recommends you still apply sunscreen to your face, even after using cosmetics and skin serum, to ensure you have protection from UV rays no matter what you’re wearing.

Too Old

You should be going through at least one bottle of sunblock in a season, but in case you do have some leftover sunscreen from last year, it’s best to toss it away. This is because sunscreen can expire.

Read: Some Sunscreens Perform Below SPF Protection Claims, Increasing Risk Of Sun Exposure

"Sunscreen must have the appropriate active ingredient to work well, which is most often avobenzone or zinc oxide. Both of those chemicals degrade over time, so it's important that they not be expired,” Dr. Joshua D. Zuckerman, MD, FACS, a board-certified plastic surgeon practicing in New York, told Medical Daily .

You Got Wet

While many sunscreens are waterproof, they can become less effective when they get wet and this water resistance can only go so far.

“As soon as you get sunscreen wet, it immediately starts to diminish the level of protection. The FDA only allows the claims 'Water Resistant (40 min)' or 'Water Resistant (80 min)' to be used on sunscreens sold in the USA,” explained Dr. Alex Roher of San Diego Botox. “ 'Water Resistant Sunscreens' retain their stated SPF value after a certain time (either 40 or 80 minutes) in water or while sweating.”

In addition, Yadav explained that simply sweating and wiping it off can cut down on the amount of time that sunblock may protect you for.

Mixing With Drugs

According to Fox News, sometimes sunscreen does not work as well if you have certain drugs in your body, such as certain acne treatments, antihistamines, and certain forms of antibiotics. In addition, alcohol can also affect the effectiveness of sunblock. Drinking can cause your body to create acetaldehyde, which in turn can make your skin extra sensitive to the sun, The Today Show reported. As a result, you may have to practice extra care if you’re drinking out in the sun.

See Also:

Broccoli Shows Promise As Viable Sunscreen; Applying The Superfood To Your Skin Could Prevent Skin Cancer

Most Highly Rated Sunscreens Fail To Meet Skin Cancer Protection Guidelines: Study