How Long After Shocking a Pool Is It Safe To Swim?

On a hot day, there's nothing quite as tempting as a cool swimming pool. A pool that hasn't been used for a while, however, needs to be prepped, or "shocked," before you can jump in and splash around or do laps.

Shocking is crucial for removing any pathogens in the water and making a pool safe for swimming, but it involves using some heavy-duty chemicals, including chlorine. Going in too soon after a pool's been shocked can potentially cause skin, eye, and even lung problems.

It's tough to wait to take a dip, but it's not worth messing with your health. Here's what to know before you take the plunge.

What Is Shocking a Pool?

If you've owned or maintained a pool, you've probably heard the term. Shocking is "the process of adding chemicals to the pool to make water composition ideal for chlorine or non-chlorine alternatives to work best," Jamie Alan, PhD, an associate professor of pharmacology and toxicology at Michigan State, told Health.

The goal of shocking the pool is to raise the level of "free chlorine" in the pool to a point where things like algae and bacteria are destroyed. (Free chlorine is chlorine that hasn't yet neutralized harmful gunk in the pool.)

There is a range of chemicals that can be used for a pool shock, including calcium hypochlorite and chlorinated isocyanurates like trichloroisocyanuric acid or potassium dichloroisocyanurate.

When Is It Safe?

In general, it's recommended that you wait up to 24 hours to get into a pool after it's been shocked, depending on the size of the pool, Alan said.

If you're overseeing the pool maintenance, Alan said it's also a good idea to test the water's pH and chlorine to make sure they're in the right range before you or anyone else gets in the pool. A good chlorine level is between 1.0 and 4.0 parts per million, and the pH should be between 7.2 and 7.8, according to the Centers for Disease Control and Prevention.

Swimming Too Soon After a Pool Shock

There are a few potential issues. "Chlorine will react with water to produce an acid," Alan said. "The effects will be different depending on whether chlorine is inhaled or whether there is skin or eye contact."

At a minimum, "you would definitely get dry skin," Gary Goldenberg, MD, assistant clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York City, told Health. And, if you happen to have a skin condition like eczema or psoriasis, Dr. Goldenberg said this could cause a flare. You may even deal with symptoms like burning, redness, pain, and blisters, Alan added.

The water can also impact your eyes and lungs. "Eye effects would include pain, redness, blurred vision, and watery eyes," Alan said. "The inhalation effects are typically the most severe and include shortness of breath, chest tightness, wheezing, and fluid in the lungs."

And, if you happen to accidentally drink some pool water, you could end up feeling nauseous and even throw up.

Luckily, Alan said, "the effects are typically reversible." If you hop into a pool too soon after it's been shocked and you start to notice symptoms, Alan said it's important to get out ASAP and get to fresh air (i.e., away from the pool). "Remove all exposed clothing and wash all the affected areas thoroughly with soap and water," Alan said. If you wear contacts, she also recommended taking them out and "thoroughly" rinsing your eyes with saline solution.

If your skin feels uncomfortable after you've cleaned off, Dr. Goldenberg recommended using a moisturizer, or a topical steroid cream if your symptoms don't improve. According to National Capitol Poison Control, if skin or eye irritation persists or worsens, or you are experiencing shortness of breath, chest tightness, or wheezing, you should seek medical attention immediately.