From itchy skin to heart attacks, the risks of a swim in the great outdoors

MINUTes after finishing my swim, my skin began to itch, and within a couple of hours my arms, legs, belly and chest were covered in unsightly red spots. I had swimmer’s itch, or cercarial dermatitis, which is caused by a parasite carried by some birds and freshwater snails which burrows into your skin, and causes a rash.

The rash appeared after a swim in the serpentine in London’s Hyde Park. I’ve enjoyed so-called ‘wild swimming’ — in lakes, rivers and the sea — for more than 20 years, and must have done it more than 100 times in the serpentine without incident, until last summer.

Thankfully, the rash is neither dangerous nor contagious, and after a few itchy nights, my spots cleared up thanks to a mild steroid cream.

But as wild swimming becomes increasingly popular — advocates say it can soothe muscle aches, boost the immune system and even relieve depression in a way that a chlorinated pool never can — it is not without hazards. Here are some other risks of bathing in the great outdoors.

Lakes, ponds and reservoirs

PerHaPs the greatest danger with freshwater swimming is the coldness of deep water.

early summer is particularly risky — below the surface water can still be very cold (it’s less of a problem in rivers or the sea, where the water moves, so the temperature contrast won’t be as great).

The risk is cold shock response, where people gasp and breathe rapidly after sudden exposure to very cold water. This can trigger a cardiac arrest in unfit people. But it’s not the only concern. ‘even strong swimmers can get into trouble trying to swim across a deep lake or reservoir — because the cold weakens their arms and legs and they find themselves far from safety,’ adds Lynne roper, a spokeswoman for the Outdoor swimming society.

If your body temperature drops too low, the body ‘will do all it can to conserve heat, starving the muscles of blood, and oxygen’, explains Isobel Kearl of st John ambulance.

another potential hazard, especially in summer, is blue-green algae. It forms a powdery green scum on lakes and ponds — this can set off an allergic rash or sore eyes. Isobel Kearl suggests washing the affected skin before taking antihistamines — and seeking further medical advice if necessary.

swimming in freshwater lakes and rivers also carries the risk of the norovirus and bacteria such as e.coli — which can cause vomiting and diarrhoea. ‘The risk is particularly acute in low-lying reservoirs or lakes near a sewage outflow,’ says Paul Hunter, a professor of health protection at the University of east anglia.

Rivers and canals

sWIMMING in canals or rivers could result in Weil’s disease ( or leptospirosis) — a bacterial infection spread by rat urine. Canals are particularly risky because the water is stagnant, as are slow-moving rivers in urban areas where the rat population is high.

But it can also be caught in lakes. You get it by swallowing contaminated water or absorbing it into the bloodstream through a cut or graze.

any cuts should therefore first be covered with a waterproof plaster, though the NHs advises against swimming in metropolitan canals at all. symptoms include high temperature, vomiting, headaches, swellings, chills and fatigue. One in ten patients suffers a severe infection sometimes affecting the liver, causing jaundice, says Isobel Kearl.

The usual treatment is antibiotics.

The sea

LasT year, the royal National Lifeboat Institution dealt with 97 jellyfish stings in British coastal waters. Most stings aren’t dangerous, but they usually cause pain and sometimes a rash.

‘remove remaining tentacles using tweezers,’ says Dr Imran rafi, of the royal College of General Practitioners. ‘and an ice pack will help ease pain and inflammation.’

Washing the affected area with seawater can help — ‘or, even better, vinegar, which nullifies the chemical reaction,’ says Isobel Kearl. But that popular DIY remedy, urine, can exacerbate the stinging pain.

Jellyfish aren’t the only stinging fish in our waters, as I can testify.

Weevers are small fish that bury themselves in the sand by the water’s edge. They have poisonous spines and gills that can sting, causing pain and then numbness.

Luckily, I was stung near a lifeguard station, in Dorset. They put my foot in a bowl of hot water (heat breaks down the venom) and after 30 minutes the pain eased off. ‘ If a weever’s spine breaks off and it’s not removed from the skin, it can cause infection,’ warns Isobel Kearl. ‘If you can’t get it out, visit the hospital.’ Despite the risks, the good news is: ‘ The more you swim outdoors, the more you build immunity to the risks,’ adds Professor Hunter.