You sweat in order to cool off your body. As sweat droplets evaporate, your skin cools down. So, if your upper lip develops sweat while eating a steaming bowl of soup or little beads run down your forehead after something super spicy, you can understand why you're perspiring. (By the way, this is an entirely normal body response, according to Merck Manual.)
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But there are also medical causes behind sweating after you eat, a term called "gustatory sweating." Here's what might be going on:
1. It’s a Specific Food You're Eating
There are specific foods known for triggering the sweat response, which may include coffee, chocolate, spicy or sour foods, hot foods, alcohol and sweets, according to the International Hyperhidrosis Society.
"I don't often hear patients say that when they eat they sweat all over their body. When I do, patients have figured out that when they eat [a certain food], they sweat," David Pariser, MD, a dermatologist and specialist in hyperhidrosis (excessive sweating) in Norfolk, Virginia, tells LIVESTRONG.com.
If you notice a certain food does it — and you've been checked out for other medical conditions by your doctor — the simplest advice holds: Avoid that food to avoid the sweat.
2. You Have Frey Syndrome
This is a rare condition that happens after facial surgery around the parotid glands, which are salivary glands below your ears, according to the National Organization for Rare Disorders. This can happen as a result of surgery from a benign or malignant tumor in the parotid gland itself, a skin cancer removal or plastic surgery, Dr. Pariser says.
What happens, he explains, is that as skin and nerves heal following surgery, branches of the nerves that went to these salivary glands may essentially become mixed up and hook up to the sweat glands in skin. As saliva glands are stimulated in response to eating, which is part of the digestive process, they mistakingly trigger sweat glands to sweat.
"This is a dripping sweat. While it's not a serious medical condition, it can be disabling socially," Dr. Pariser says.
It's almost sure to happen if you had surgery on a parotid gland, though it's rare in cases of plastic surgery, he says. Most cases of Frey's involve just one side of the face.
As for treatment, "Botox injections are the most effective and easiest treatment," Dr. Pariser says, adding that results usually last nine to 12 months, and up to two years.
While this is a first-line treatment for Frey's, there can be issues with insurance coverage (the treatment is off-label), though some companies will cover it. Regardless, while the upfront cost of Botox may be higher compared to medications, in the long-run, it can be more cost-effective for patients, Dr. Pariser says.
3. You Have Nerve Damage From Diabetes
People who have diabetic autonomic neuropathy — a complication of diabetes involving nerve damage — may sweat on the forehead, face, scalp and neck after chewing food, particularly after eating cheese.
"What I tell patients is that there's nothing the matter with their sweat glands, it's the switch that controls them," Dr. Pariser says. In this case, that switch is stuck to on, and nerves are stimulating sweat when they otherwise shouldn't be.
4. You Have Shingles
This is a reactivation of the varicella-zoster virus, the one that causes chickenpox. It can cause a rather painful rash, and if this rash is on your face, then the nerves can be damaged, leading to gustatory sweating, notes Merck Manual.
This is known as secondary hyperhidrosis, according to the International Hyperhidrosis Society. You'll likely sweat on both sides of the face as well as your neck and chest. You might have this response when you eat or even just think about food, according to the organization.
Treatment for shingles includes antiviral medication, so see your doctor if this is happening to you.
5. It's a Symptom of Parkinson’s Disease
This is a progressive brain disorder that causes shaking, makes walking difficult and affects balance, according to the National Institute on Aging. Both brain and nerve disorders are linked to sweating conditions.
If the cause of sweating after you eat is a side effect of a medical condition, you should be properly treated by your primary care provider or another specialist who can treat the underlying condition and provide specific suggestions for how to manage any sweating side effects.
- Merck Manual: “Excessive Sweating”
- National Organization for Rare Disorders: “Frey Syndrome”
- International Hyperhidrosis Society: “Gustatory Hyperhidrosis/Frey’s Syndrome”
- International Hyperhidrosis Society: “Gustatory Sweating (Frey’s Syndrome)”
- Journal of Neurology, Neurosurgery and Psychiatry: “Diabetes mellitus and the nervous system”
- National Institute on Aging: “Parkinson’s Disease”