Diabetes: Why Am I feeling Hot After Eating?

Excessive sweating may occur for several reasons. If you find that your sweating has increased since you've been diagnosed with diabetes, this may be because there are a couple of forms of hyperhidrosis (excessive sweating) that have been linked to the disease. 

Your doctor will be able to help you determine whether your sweating is natural or whether diabetes or some other condition, may be at fault. Except for extreme cases, treatment options are simple and non-invasive.

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Why humans sweat

Humans are one of few mammals that are capable of removing excess heat through the use of sweat glands. While sweating is most commonly associated with hot weather, it serves two purposes within the body. To fully understand the process, let's look at both of them.

  • Thermoregulatory - Your body can get too hot for a number of reasons. The sun beating down on a hot day is a common cause, but physical exertion also raises your body temperature. When your body gets too warm, the eccrine sweat glands tell your body to release sweat. Eccrine glands are the sweat glands that cover most of your body, as opposed to apocrine sweat glands, which are found primarily around hair follicles. As the sweat from the eccrine glands begins to evaporate, your body temperature cools. This type of sweating is controlled mostly by a part of the brain called the hypothalamus.

  • Emotional - You can also start sweating in response to emotional stimuli. The mechanism for this type of sweating takes place largely in the limbic region of the brain. Emotional sweating tends to be limited to the face, armpits, palms, and soles of the feet. Although it's a different mechanism than thermoregulatory sweating, the two mechanisms do influence one another.

What is excessive sweating?

Sweating is a normal, and important, part of being human. In severe situations, your body will even sweat quite a bit. However, in some people, the body produces extreme levels of sweat without an underlying extreme cause. This condition, known as hyperhidrosis, can be annoying, embarrassing, and uncomfortable.

There are several types of excessive sweating and several underlying causes that may be at the root of the issue. 

Types of excessive sweating

The medical name for excessive sweating is hyperhidrosis. There are two major types of hyperhidrosis, generalized and focal. 

Generalized hyperhidrosis can be caused by conditions such as infection, endocrine imbalances, medications, intoxication, and withdrawals from alcohol or other substances. Generalized sweating affects the whole body. 

The second type of excessive sweating is called focal hyperhidrosis. This type of sweating can be broken down into four categories:

  • Primary focal hyperhidrosis - This form of hyperhidrosis often develops during puberty. It's also the most common form of the condition, making up over half of all cases. Primary focal hyperhidrosis affects mainly the armpit area, but can also impact the face, hands, and feet as well. In many cases, there's a family history of the condition among those who suffer from it.

  • Secondary focal hyperhidrosis - This type of hyperhidrosis is caused by damage to the nervous system. This can include nerves in the brain, or peripheral nerves outside the brain. Sweating of this nature is one of the many symptoms that can be a sign of other conditions, such as post-traumatic syringomyelia, which is the development of a cavity in the spinal cord filled with spinal fluid.

  • Harlequin syndrome - When a person develops Harlequin syndrome, one side of their face suffers nerve damage that prevents it from sweating properly. As a result, the other side of the face develops hyperhidrosis as a way of compensating for the reduced sweating. The result is one half of the face appearing dry and pale, while the other is moist and red.

  • Frey's syndrome - The parotid gland is a major salivary gland located below the ear. Damage to this gland can result in Frey's syndrome. Those who develop the condition sweat excessively after eating, or even thinking, about food. The sweating occurs around the area of the parotid gland: the cheek, temple, and ear area. Sweating triggered by food intake is known as gustatory sweating.


If you're sweating excessively, your doctor will first ask you about your medical history and may run some tests to see if any underlying causes might be causing you to sweat too much. Specific tests to check for and narrow down the specific type of hyperhidrosis can include an iodine starch test.

With this test, iodine is applied to the skin, and starch is placed on top of it. The solution will turn a purple color when it comes in contact with sweat. This test allows doctors to see exactly where you are sweating and what the pattern looks like.

Doctors can measure the amount of sweat by placing a pre-weighed piece of filler paper over the affected area and then measuring again after it's been allowed to come in contact with the sweat. This information, along with the pattern exposed by the iodine starch test, can help doctors narrow down the severity and type of hyperhidrosis.

How is diabetes related to excessive sweating?

One of the risk factors for generalized hyperhidrosis includes endocrine imbalances. As diabetes is a disease affecting the endocrine system, it can be a cause of generalized hyperhidrosis.

Diabetics who are experiencing generalized hyperhidrosis will typically sweat all over, but diabetes is also a risk factor for a type of focal/gustatory hyperhidrosis, that is limited largely to the face, head, and upper body, though can also affect the whole body.

Diabetics who are experiencing this form of hyperhidrosis will notice the extra sweat after eating.

Why do I feel hot after eating?

Frey's syndrome isn't the only condition that can cause gustatory sweating. In some instances, the response is normal. For example, eating extremely spicy foods may trigger your body to begin sweating.

However, some people sweat profusely after eating, even when foods that would trigger the condition aren't being consumed. This is a well-known side effect of diabetes mellitus, affecting twice as many diabetics as non-diabetics. At the moment, researchers are unsure of the exact pathophysiology that results in the condition among diabetics.

Hyperhidrosis treatment

Often, hyperhidrosis doesn't require treatment, but many people find that excessive sweating has detrimental effects on their confidence and social lives. There are some medical options available that can reduce the sweating and allow those with hyperhidrosis to live a life they're more comfortable with. These methods include medication, and in extreme cases, surgery.


Medications that alleviate hyperhidrosis symptoms come in both systemic and topical forms. The most common options your doctor may try are listed below:

  • Anticholinergic drugs - This class of drugs has shown to be effective against hyperhidrosis. Side effects, which include, dry mouth, urinary retention, and memory problems are a limitation to more widespread use, however.

  • Antihypertensive drugs - Several drugs used to treat hypertension, such as beta-blockers and calcium channel blockers, are moderately effective at treating certain types of hyperhidrosis.

  • Antidepressants - Similarly to antihypertensive drugs, some antidepressants have shown to have a mild effect on reducing excessive sweating caused by hyperhidrosis. 

  • Prescription antiperspirant - Most over-the-counter antiperspirants use aluminum salts at a concentration of around 1% to 2%. Prescription antiperspirants can go much higher, with concentrations reaching 25%.

  • Glycopyrrolate cream - Another topical option is glycopyrrolate cream. The substance is an anticholinergic that's particularly useful in gustatory sweating, such as that caused by Frey's syndrome or diabetes.

  • Botulinum toxins - Injection of botulinum toxins to inhibit the release of acetylcholine is the most effective method of controlling focal hyperhidrosis. The injections are typically effective for 4-7 months.


Treating hyperhidrosis with surgery is considered a last resort that should only be used when all other options have been exhausted. The two surgical procedures often used involve removing either the nerves responsible for the reaction or removing the sweat glands themselves.

Removal of the nerves ( sympathectomy) is most effective in sweat coming from the palms of the hands. Removal of the sweat glands is most effective in the armpit area, but is not a trivial operation and may cause complications such as infection, scarring, and skin necrosis or discoloration.

When should I see a doctor?

Seeing a doctor as soon as you notice that you're sweating more than you usually do can help ensure that no underlying conditions are causing this. Your doctor can prescribe medications that will help reduce the severity of the sweating. If you've recently developed diabetes, the conditions may be linked, and a doctor will be able to determine this connection. 

The lowdown

There are several reasons your body may begin to sweat more than usual. A few of them may be related to your diabetes diagnosis. If you find yourself noticeably sweating more than usual, consult your doctor. An examination will help you determine the cause of the sweating and find the treatment option that best suits you.

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