Ask Our Community: NMO and Heat Sensitivity

Increases in body temperature can worsen symptoms of neuromyelitis optica spectrum disorder (NMO). This worsening of symptoms with heat is called Uhthoff’s phenomenon.^1-3

How does heat impact NMO?

Although the exact cause of Uhthoff’s phenomenon is not known, there are some theories. Experts believe that increases in body temperature may impact the way nerves talk to one another.^1,2,4

NMO is an autoimmune condition in which the body mistakenly attacks its own healthy nerves. This makes it harder for nerves to communicate with one another and leads to symptoms. If nerves are already damaged and have a hard time talking to each other because of NMO, increases in temperature may make things even worse.⁶

Studies have shown that even small increases in body temperature can impact nerve conduction speed (how fast nerves talk to each other and other parts of the body). Exercising, sitting outside in the sun, having a fever, or taking a hot bath can all cause these small changes. Increases in body temperature may also lead to more inflammation. Proteins related inflammation can lead to additional symptoms like fatigue and pain.²

In some cases, Uhthoff’s phenomenon can occur even before a person is diagnosed with NMO or MS.²

Many of our community members report their NMO symptoms worsening in the heat

"I live in Arizona, and I can handle the heat at 110 degrees, but not when it's 80 degrees and humid. Nausea, confusion, and crabby!"- Christine

"I work 12-hour shifts in a building with no air conditioning. It is around 90 degrees or more all year long. I get so sick, it's horrible."- Shawna

"I pass out in 70-degree weather."- Sandra

"Could this be why I'll suddenly feel as if I'm in a 400-degree oven? If I don't get the fan on me immediately I sweat profusely. My ears get bright red, I have blurred vision and usually headaches but not nausea."- Kathy

"I got my very first MS hug when transitioning from a cold atmosphere to hot. I go for pool therapy, but they keep the pool at 82 degrees. The heat also drains my energy real bad. A/C is my friend in the summer."- Bonita

This includes two of our neuromyelitis-optica.net advocates, Mo and Aldelly

"I notice vision changes when I get hot."- Mo

"For me, heat intolerance is a real thing. I hadn’t realized that my exacerbations were occurring because of the summer weather, or that the extreme cold temperatures of New England were causing me so much pain in my body. Observe what temperature works for your body and try your best to adjust." - Aldelly

Others report reactions to changes in temperature in general

"This is me. Except reversed, it's the cold that my body has issues with."- Tiffany

"I have problems with heat and cold. Heat and humidity cause me to swell all over but mostly in my feet, legs, fingers, and face. However, when cool or cold air hits my body whether it hits my feet, arms, or face, it causes pain. Even the slightest breeze will cause pain."- Melissa

Some of our community members say their temperature sensitivity is triggered by everyday activities, like eating or cleaning the house

"Mine is associated with eating, it is an awful feeling, starts at my feet and works up to my head, the heat gets so intense and my face gets red."- Janet

"I noticed that when I just do a little bit of cleaning, like sweeping the kitchen floor, I don't sweat until I stop and sit down."- Sharon

So what can we do about heat sensitivity in particular?

Although heat may worsen symptoms, it does not mean certain activities should be avoided. Exercising may actually help improve symptoms. It can also help prevent other co-occurring conditions from arising and causing more issues.⁷

• Drinking plenty of cold water
• Taking cool showers or baths when feeling warm
• Staying in the shade when outside
• Spending time outdoors in the morning or evening when temperatures are cooler, rather than during mid-day when it is hotter
• Seeing your doctor right away if you think you have a fever or infection
• Staying with a buddy when working out or spending time outdoors in the sun
• Limiting time in hot water, such as hot showers or hot tubs

Some research has suggested that using cooling methods before and during exercise may help. These include using cool compresses or cooling vests. Talk to your doctor about any limitations you may have with NMO when it comes to exercise or being outside.⁷

If you have symptoms of Uhthoff’s phenomenon but were not doing an activity that raised your body temperature before symptoms began, talk with your doctor. An underlying infection causing a fever can increase your body temperature, too. Your doctor can help figure out if your symptoms are related to something causing Uhthoff’s phenomenon or another separate issue.^1,2,4

Do you have sensitivity to heat or cold?

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