Heat Intolerance

Heat intolerance is a symptom that makes it easier for you to overheat in warm or hot environments. Having it means your body can’t tolerate or adapt to heat as the average person’s body can. Heat intolerance isn’t just unpleasant — it can actually be dangerous.

Heat intolerance is more than just not liking feeling hot. It’s a symptom that can happen with many medical conditions. Most of them need medical care, and a few are serious. And several medications — including some widely used ones — can also cause it. Your age can make heat intolerance more likely, too.

How heat intolerance affects you

When you’re too hot, your body has processes to help you cool off. Your autonomic nervous system manages these automatically.

Some cooling processes include:

• Widening capillaries under your skin, letting blood from your body’s core shed heat as it flows through them
• Sweating
• Breathing faster, so your exhales carry extra heat out of your body
• Slowing your metabolism
• Making you feel more thirsty and less hungry
• Making you feel tired or sleepy, so you move less and don’t generate as much body heat

But if you have heat intolerance, your body may not do these things. That can make your internal temp rise too high. Overheating can make you sick, like with heat exhaustion. And in severe cases, it can even cause heat stroke, which can be deadly.

What heat intolerance looks like

People with heat intolerance can overheat more easily. That can cause or look like:

• Sweating very hard (hyperhidrosis) or not sweating enough
• Skin color changes, like flushing
• Seeming lethargic or unusually tired
• Trouble concentrating when it’s hot, confusion or mental state changes

Heat intolerance causes

Heat intolerance can happen with several medical conditions. It’s also a possible side effect of some very common medications. Your age can contribute to heat intolerance, too.

Conditions that can cause heat intolerance

Heat intolerance can happen with the following kinds of conditions:

• Nervous system conditions: These are like having a broken thermostat. Your body either can’t tell it’s too hot or can’t adjust the temperature setting. This includes conditions like diabetes-related neuropathy or dysautonomia.
• Brain or spinal cord injuries: These can affect your body’s temperature control if they damage your hypothalamus or cut off signaling to and from it. That’s where your body’s internal thermostat is.
• Autoimmune and inflammatory diseases: Inflammation from these diseases can disrupt many body systems, especially your nervous system. Examples include lupus, multiple sclerosis and Sjögren’s syndrome.
• Endocrine conditions: These affect your metabolism. If your metabolism is too high, it’s like revving an engine so it overheats. Hyperthyroidism, including conditions like thyrotoxicosis or Graves’ disease, are examples.
• Obesity: Having overweight or obesity means your body has to work harder when you move around. That generates more heat. And at the same time, your body is less effective at shedding heat.
• Genetic diseases: Fabry disease can cause heat intolerance. You can inherit this disease from one or both biological parents.
• Menopause: This can affect your body’s temperature regulation, making it overact to temperature changes. That’s what causes hot flashes and chills.
• Tumors and cancers: These can cause effects similar to endocrine or nervous system conditions.
• Previous heat-related illness: Having heat stroke can affect your body's internal temperature control. That can make you develop heat intolerance and make heat stroke more likely to happen again.

Medications and heat intolerance

Several types of medications can cause heat intolerance. The most common types include:

• Allergy and antinausea medicines
• Antidepressants and anxiety medicines
• Antipsychotic and schizophrenia medicines
• Antiseizure medicines
• Blood pressure medicines
• Blood thinners
• Parkinson’s disease medicines
• Stimulants

If you aren’t sure whether a medicine you take might affect your heat intolerance, talk to your healthcare provider or pharmacist. They can help you learn more and offer guidance.

Age and heat intolerance

Heat intolerance is more likely in infants and in older adults. That’s because their bodies have to work harder to maintain internal temps.

Many older adults with chronic conditions have an even higher risk of heat intolerance. That’s because some of the most common medications for age-related conditions also cause heat intolerance. That includes medicines for blood pressure, Parkinson’s disease and more.

How is heat intolerance treated?

There isn’t a direct treatment for heat intolerance. But there are two ways to treat it indirectly:

• Treating the underlying condition
• Managing the effects of heat intolerance

Treating the underlying condition

Managing a condition that causes heat intolerance can make it easier for your body to handle higher temperatures. But the treatments can vary greatly. The condition you have, medications you already take and your health history can all factor in. Your healthcare provider can tell you more about your options.

Managing the effects of heat intolerance

You can’t always control the temperature or how heat affects you. But you can still take steps to protect yourself and your loved ones. Some things you can do include:

• Pay attention to the forecast. Knowing when it will be hot can help you plan.
• Stay out of the sun. Staying indoors where it’s cool can help immensely. Blinds and drapes can also limit how much the sun heats the inside of your home.
• Don’t push yourself. Physical activity makes you generate more heat. Taking it easy can help you avoid overheating.
• Know where you can go. If it’s too hot in your home, head for somewhere public that’s air-conditioned. Some places have dedicated cooling centers that open up during heat waves. And public buildings like libraries can also offer some refuge from the heat.
• Hydrate. Fluids can help your body cool itself. But don’t reach for anything with caffeine or alcohol in it. Both make you pee more, which can dehydrate you.
• Check on loved ones and neighbors. Check on older adults you know to make sure they’re safe from the heat.

Talking to your healthcare provider about your medications is also a good idea. They can help you understand the effects of the medicines you take. And they can guide you on how to prevent or limit any unwanted effects, like heat intolerance.