If eczema behind the knees seems to flare up after swimming, you’re definitely not imagining it, and chlorine is very likely part of the reason. Here’s what’s actually going on, and what genuinely helps.
Why Behind the Knees, Specifically?
The crease behind your knees is what’s called a flexural site, one of the classic spots where eczema loves to show up, right alongside the inner elbows, the front of the ankles, and the neck. These folded areas already trap moisture and get more friction than flatter skin, so this spot is primed to flare even before chlorine gets involved.
What Chlorine Actually Does to Your Skin
A well-balanced pool typically sits at a pH between 7.2 and 7.8, just a bit higher than your skin’s naturally more acidic pH. That mismatch, combined with chlorine’s drying effect, can strip away the oils your skin barrier depends on, leaving it more vulnerable right after you get out.
The Real Culprit Might Not Even Be Chlorine Itself
Here’s something worth knowing: a lot of the irritation people blame on chlorine actually comes from something called combined chlorine, or chloramines. These form when chlorine reacts with sweat, urine, and other organic matter in the water, and they’re the real source of that sharp “pool smell” and red, stinging eyes, not the chlorine on its own.
Here’s the Honest, Slightly Confusing Part
The research on chlorine and eczema is genuinely mixed, and it’s worth just saying so instead of pretending there’s one clean answer. Some people find chlorinated water actually calms their eczema down, kind of like how dermatologists sometimes recommend a dilute bleach bath as an actual treatment. Other research, including data on lifeguards and frequent swimmers, points the opposite way, showing that repeated pool exposure measurably increases water loss from the skin and is tied to higher rates of eczema and irritation over time.
The honest takeaway: how your skin responds to chlorine is genuinely personal. It’s worth watching your own pattern rather than assuming it’ll go one way or the other.
Your Wet Swimsuit Is Part of the Problem Too
Easy to overlook this one: a chlorine-soaked swimsuit sitting against your skin after you get out of the pool keeps irritating you long after you’ve left the water. Changing out of wet swimwear as soon as you reasonably can makes a real difference.
Your Swim Day Checklist
| Before You Swim | After You Swim | |
|---|---|---|
| Rinse | Quick shower with fresh water to reduce chlorine absorption | Rinse with fresh water right away |
| Protect | Apply a thick barrier ointment, like petroleum jelly or a ceramide-rich cream | Change out of your wet swimsuit as soon as you can |
| Moisturize | Not needed at this stage | Moisturize once you’re dry, using something like Dermasolve’s Eczema Cream, within the same short window that matters after any bath or shower |
We cover the right way to layer that routine here if you want the full breakdown.
When to See a Dermatologist
- Flares behind the knees keep getting worse despite these precautions
- You’re not sure whether chlorine is actually your trigger or something else about the pool environment
- The area shows signs of infection, like increased warmth, swelling, or oozing
- You want guidance on whether a dilute bleach bath might actually help your specific case
Swimming doesn’t have to be off the table with eczema; it just usually takes a little more preparation before and after.
Mike Marenick is the founder of HealFast Skincare and holds the patent for his invention, Ovasome Technology, used in skincare formulations. He began developing skincare products after watching his mother manage psoriasis for decades, and has spent over twenty years formulating treatments for chronic skin conditions. His work has been featured on Home Shopping Network, in two national infomercials, and in more than 300 publications including Vogue, Newsweek, and Allure. He is not a medical doctor — always consult a dermatologist for diagnosis and treatment of skin conditions.
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