Summer usually means more pool days, more sunscreen, and more time in chlorinated or salt water, all of which touch sensitive skin far more than usual. Some people notice their skin reacts after swimming, others don't notice a thing. A quick note after each swim is the simplest way to find out which one you are.
Chlorine, salt water, sun cream, and just being wet and dry again and again in one day are all a lot for skin to handle at once. It's easy to blame "the pool" in general without ever writing down the actual details, so a pattern (or the lack of one) stays invisible.
A single itchy evening after the pool could be anything. What's useful is comparing several pool days against several non-pool days over the same few weeks, so you can see whether swimming actually lines up with flares for you, or whether something else was really going on.
Some people do better in the ocean than a chlorinated pool, others find the opposite, and plenty of people notice no real difference at all. There's no single rule that applies to everyone, so tracking your own summer is the only way to know your own pattern.
This is general, practical information, not a diagnosis or treatment recommendation. If a reaction seems severe or doesn't settle down, it's always worth talking to a doctor or dermatologist.
This is exactly what I built SkinFam for, a private, on-device diary for eczema and skin flare-ups. Log a pool day alongside the weather, sun cream, and how your skin felt, and nothing you write ever leaves your phone. Search "SkinFam" on the App Store.