Sunburn, Heat Rash and Chafing: Professor Caitriona Ryan's Guide to Irish Summer Skin Problems

Irish skin is particularly vulnerable to summer conditions. Sunburn, heat rash, polymorphic light eruption, chafing and fungal infections all spike when the weather turns warm. Professor Caitriona Ryan, Consultant Dermatologist and Co-founder of the Institute of Dermatologists, explains the causes and what you can do to protect your skin this summer.

In a recent interview with Katie Hannon and Colm Ó Mongáin on RTÉ Radio 1's Drivetime, Professor Caitriona Ryan, Consultant Dermatologist and Co-founder of the Institute of Dermatologists, answered listener questions on the skin problems that flare up the moment Irish weather turns warm, from sunburn to a surprisingly common condition most sufferers have never had properly explained to them.

Irish skin isn't built for sudden heat and sun exposure, and it shows. Sunburn, heat rash, polymorphic light eruption, chafing, athlete's foot and mosquito bites all spike as soon as the weather turns warm. Most are preventable with a few consistent habits: sunscreen actually applied and reapplied, breathable fabrics, and treating fungal or allergic reactions early rather than waiting them out.

Why Don't Irish People Take Sunscreen Seriously?

Professor Ryan is direct about this. We still don't. "I'm always shocked at the amount of people who get sunburnt in Ireland," she says. Irish holidaymakers are often diligent about sunscreen abroad, reapplying and seeking shade, but that discipline tends to disappear at home. One of the most common places she sees sunburn in her own patients is somewhere unglamorous: a beer garden or back garden, hours spent outside without a second thought to reapplying SPF.

"I'm always shocked at the amount of people who get sunburnt in Ireland."
Professor Caitriona Ryan, Institute of Dermatologists

The lesson is simple but easy to ignore. UV exposure on an ordinary warm day in Ireland is still UV exposure, and it adds up the same way a beach holiday does.

What Causes Heat Rash in Warm Weather?

There are two distinct things people call "heat rash," and they're worth telling apart.

The first is an occlusive sweat rash: tiny, intensely itchy bumps that appear after a day spent in the heat. It's driven by trapped sweat rather than sun exposure directly, and can be made worse by thick sun lotions sitting on the skin. It's common in young children and babies too.

The second is less well known, and far more disruptive for the people who get it.

What Is Polymorphic Light Eruption, and Why Do So Many Irish People Get It?

Polymorphic light eruption (PLE) is an itchy rash that typically appears three to five days into a holiday, on the arms, legs and sometimes the chest, but almost never the face, since facial skin has usually built up some tolerance to UV over the year. It affects an estimated 22% of Irish people, and is especially common in Celtic skin types. It's frequently mistaken for a sun cream allergy.

Key stat: Polymorphic light eruption affects an estimated 22% of Irish people and is especially common in Celtic skin types.

One listener wrote in describing how disruptive PLE can be even with active management. Daily antihistamines, prescription treatment and light therapy were already in place, and she was still losing days of a family holiday to a flare after only brief sun exposure.

Professor Ryan's approach for patients prone to PLE: start an antihistamine on day one of the holiday, before symptoms appear. Keep a topical steroid on hand to treat any rash that does break through. Where possible, wear light, loose-fitting clothing that physically blocks UV from reaching the skin in the first place. She also notes that symptoms tend to ease as the summer goes on, as skin gradually builds up tolerance to repeated sun exposure.

If you suspect you have PLE and it's significantly affecting your quality of life, a consultation with a dermatologist is a reasonable first step, particularly if over-the-counter measures aren't enough.

How Can You Prevent Chafing in Hot Weather?

Chafing happens year-round but is far more common in summer, when heat and sweat increase friction. The most affected areas are the inner thighs, under the breasts (particularly for those with larger breasts), and underarms.

Professor Ryan's practical advice: apply Vaseline to areas prone to friction, such as the inner thighs, before exercise. Choose a supportive, well-fitted sports bra to limit movement-related friction. Look for underwear and activewear without prominent seams where friction occurs, and favour cotton or sweat-wicking fabrics that pull moisture away from the skin. Seamless "anti-chafing" underwear, now widely available, is specifically designed to remove the stitching that causes irritation.

How Do You Prevent and Treat Athlete's Foot in Summer?

Fungi thrive in warm, moist environments, which makes summer feet a prime target. Socks play a bigger role than people assume. Their main function is absorbing sweat, so going sockless in runners can work against you. A foot powder can help keep the environment dry.

Treat athlete's foot quickly once it appears. Left untreated, it commonly spreads, including, in men, to the groin when trousers are pulled on over an infected foot, causing what looks like a friction-based groin rash but is actually the same fungal infection. Topical antifungal treatment (such as terbinafine, sold over the counter in Ireland) is an accessible first-line treatment.

One myth worth retiring: seawater does not treat athlete's foot. There's no scientific basis for it. A fungal infection needs an antifungal treatment, not a dip in the sea.

Why Do Mosquitoes Bite Some People More Than Others?

If you feel like mosquitoes single you out, you may be right. People with blood type O are bitten most often, followed by type B, then type A. Larger body size and pregnancy both increase attractiveness to mosquitoes, since both increase the amount of CO2 a person exhales, and mosquitoes use exhaled CO2 to locate a target. Sweat and alcohol also increase attractiveness. Even a single beer measurably increases how often you're bitten.

Some people also have a hypersensitivity reaction to bites, producing much larger, more inflamed bumps than the average reaction. This is a reaction intensity difference, not a sign of being bitten more often.

For prevention: DEET-based repellents are effective, but should not be applied directly to children's skin. Apply to clothing instead where possible, since it can be irritating on skin generally. Showering after sweating helps, since mosquitoes are also drawn to sweat. And since mosquitoes are most active at night, closing windows and doors after dark makes a meaningful difference.

Frequently Asked Questions

Does salt water help treat athlete's foot?

No. There is no scientific evidence that seawater treats a fungal infection. Athlete's foot needs a topical antifungal treatment.

Can polymorphic light eruption happen every summer?

Yes, it's a recurring condition for many people, often appearing early in the holiday season. Symptoms typically ease later in the summer as skin builds tolerance to UV exposure.

What blood type do mosquitoes prefer?

Type O is bitten most frequently, followed by type B, then type A. Larger body size, pregnancy, sweat and alcohol consumption also increase how attractive you are to mosquitoes.

Is Vaseline effective for preventing chafing?

Yes. Applying it to friction-prone areas like the inner thighs before activity is a simple, effective way to reduce chafing.

Can children use DEET insect repellent?

DEET should not be applied directly to children's skin. Apply it to clothing instead, and choose age-appropriate repellents for young children.