Surprising Causes of Hives

Stress

Stress is a relatively common cause of hives. When you’re stressed, your body releases adrenaline, which in some people can trigger hives. Not surprisingly, the advice on how to avoid stress-induced hives focuses on relaxing. If possible, take some things off your to-do list or carve out some time every day to go on a walk or read. Because you can’t live a completely stress-free life, you can also use antihistamines when you need them.

Exercise and extreme heat

If you get hives when your core body temperature rises, either from taking a hot bath, exercising, or going outside in extremely hot weather, you have what’s known as cholinergic urticaria. Anything that makes you sweat can trigger them, even eating spicy foods if they raise your body temperature enough.

It’s thought that the hives are triggered by the sweating process, with one theory being that there is a blockage and the sweat leaks into skin tissue, triggering hives. It happens to around 5% of people with hives. Try to avoid things like hot tubs, saunas, super spicy foods, and hot yoga. Your medical provider may recommend taking an antihistamine to help.

Sunlight

Hives can be caused by exposure to sunlight if you have a type of sun allergy known as solar urticaria. It is fairly uncommon and experts don’t know exactly why the sun’s ultraviolet rays trigger a reaction. While it’s impossible to avoid the sun entirely, if you think you have this allergy try to limit how long you’re outside when the sun is at its strongest, which is between 10 am and 4 pm. Also wear SPF 30 sunscreen, even on cloudy days, and long-sleeve shirts and hats to boost your protection.

Extreme cold

Exposure to frigid temperatures can also bring on hives. Cold urticaria, which is rare, is when you have hives within minutes of being out in cold weather or swimming in cold water. It’s often brought on by a sudden change in temperature, like going from being inside a warm building to outside in frigid air or jumping into a cold lake.

It’s most common in young adults. Experts think it is caused by extra sensitive skin cells that trigger the immune system when temperatures get too extreme. If you have cold urticaria, try to avoid extremely cold air or water and talk to your healthcare provider about taking antihistamines.

Physical pressure

Hives can appear after you’ve had extended pressure on your skin, like when wearing a tight belt or constrictive clothing all day. They can also occur on the bottoms of your feet if you’ve been standing or walking for a long time. Or on your buttocks if you’ve been sitting for a long time on a hard seat. Sometimes scratching can also bring on hives. The immune system triggers the release of histamines as a result of the pressure for unknown reasons.

Pressure hives occur in about 5% of people with hives. If you’re susceptible to pressure hives, try to avoid tight-fitting clothing and choose looser items. Antihistamines aren’t as effective against this type of hive.

Vibrations

Anything that repetitively stimulates your skin—pushing a lawnmower, clapping your hands, going on a bumpy ride in a car—can bring on vibratory urticaria, or vibration-induced hives. These hives tend to last only an hour or so and appear right away. This form of hives is rare and seems to be caused by a genetic mutation that allows vibrations to disrupt the skin’s mast cells more easily than they should. These hives are short-lived. Besides avoiding the trigger, they are likely something you will have to live with. Antihistamines may be helpful in some cases.