As the relentless heatwave rumbles on, it might be tempting to jump in a cold shower to bring your temperature down.But experts have warned a chilly rinse might not actually help you cool off at all – and that bathing in lukewarm water is actually more effective.Adam Taylor, a Professor of Anatomy at Lancaster University, explained that it's all to do with how our blood vessels react to changes in temperature.'Although diving into a cold bath or shower straight after being out in the heat might feel nice on your skin, it isn't doing what is needed to reduce the core temperature of the body,' Professor Taylor wrote on The Conversation.Our body's optimal temperature is around 37°C, he explained. When our core gets too hot several mechanisms kick into place to help us cool down.One important response is our blood vessels dilating, to allow more blood to get closer to the relatively cooler surface of the skin.'When exposed to cold [such as a cold shower] the blood vessels near the skin constrict, reducing the blood flow into these areas,' Professor Taylor said.'Basically, you're tricking your body that it doesn't need to cool down, but actually needs to conserve heat. This will hold the heat in and around your organs instead of getting rid of it.' Experts have revealed a chilly rinse might not actually help you cool off at all – and that bathing in lukewarm water is actually more effective (file image) It comes as the UK's hottest May day record was broken for a second day in a row this week, with warm temperatures expected to continue into tomorrow and FridayIt comes as the UK's hottest May day record was broken for a second day in a row this week.Kew Gardens in south-west London recorded a provisional temperature of 35.1°C yesterday, beating Monday's 34.8°C record-high in the same place.While temperatures like this feel fine on holiday, they can quickly become unbearable in the UK as infrastructure and buildings were historically designed to retain warmth.As a result, many people have turned to ice baths or cold water plunges in a bid to cool off.But sudden exposure to very cold temperatures could even trigger dangerous consequences for some people, Professor Taylor warned.Submerging yourself in water that is 15°C or under can trigger the cold shock response, which causes the blood vessels in the skin to constrict rapidly.This increases blood pressure and can be particularly dangerous for people with underlying heart conditions such as coronary artery disease.'Thankfully, these events are rare and probably won't happen if you're just taking a cold shower or bath in your home,' he said. 'But you might want to skip the cold plunge or avoid taking an ice bath on a hot day for this reason.' These temperatures can quickly become unbearable in the UK as our buildings are historically designed to retain heat - meaning many flock to the beach for a cold dip Experts have warned climate change is making UK heatwaves more frequent, more intense and longer lasting. Pictured: A woman uses an electric fan to cool down in London Why doesn't a cold shower cool you off? When you have a cold shower, the blood vessels near your skin constrict.This reduces blood flow into these areas, trapping heat around your organs instead of getting rid of it. A warm shower, on the other hand, causes our blood vessels to dilate and allows more blood to get closer to the cooler surface of the skin. A tepid or lukewarm bath or shower, at 26-27°C, is most effective, scientists say. While cold showers aren't advised, hot showers also aren't the way forward on a warm day, he said.Water that is warmer than the body will transfer heat to the body, potentially increasing its core temperature.A tepid or lukewarm bath or shower, at 26-27°C, is most effective, he said.Another reason to skip a cold shower on a hot day is that it might not get you fully clean.Cold water has been shown to be less effective at removing and breaking down sebum and bacteria on the skin compared to warmer water.This means that body odour could persist, and trapped dirt within pores could lead to blackheads, whiteheads and acne.Warm or lukewarm water however, can help dissolve and loosen material in the pores.A recent study revealed how often people should be washing their hair – and it's bad news for those who hate shampooing their locks.According to the experts, your hair is usually happiest and healthiest when it is washed five or six times per week.In one trial, researchers found that washing almost every day led to the best scalp condition and the most 'great hair days'.While researchers caution that the exact frequency will depend on hair type, they suggest that worries about 'overwashing' are unfounded.Dr Shilpi Khetarpal, board–certified dermatologist at the Cleveland Clinic, warns: 'When the hair and scalp are not cleaned frequently enough you can get an overgrowth of bacteria and yeast.'