The body uses perspiration to regulate its core temperature, a process controlled by the nervous system. When heat or physical exertion raises the internal temperature, sweat glands release moisture, which cools the skin upon evaporation. While this process is reliable for most people, the relationship between diabetes and sweating is complex. The chronic effects of elevated blood sugar can disrupt the nervous system’s control over these functions, leading to abnormal patterns of perspiration that range from excessive to absent.
Altered Sweating Patterns in Diabetes
Diabetes often causes two opposing types of sweating irregularities. One common manifestation is anhidrosis, the reduced or complete absence of sweating. This typically begins in the lower extremities, such as the feet and legs, resulting in a lack of evaporative cooling in those areas.
To compensate for this localized lack of perspiration, the body attempts to dissipate heat through unaffected regions. This leads to compensatory hyperhidrosis, or excessive sweating, which tends to occur in the upper body (face, neck, and torso). This pattern means an individual may have dry feet while simultaneously experiencing profuse perspiration on their forehead or chest.
The Role of Autonomic Neuropathy
The chronic reason for these altered sweating patterns is damage to the nerves that control involuntary body functions, known as autonomic neuropathy. This nerve damage affects the sudomotor system, which signals the sweat glands. Sustained high blood sugar levels can harm the small nerve fibers and blood vessels that supply these autonomic nerves.
When nerve fibers leading to sweat glands in the lower body are damaged, the signal to produce sweat is interrupted, resulting in anhidrosis. Conversely, this nerve damage can mistakenly cause sweat glands in the upper body to become overactive, leading to compensatory hyperhidrosis. This disruption creates an inefficient cooling system.
A localized manifestation of this autonomic dysfunction is gustatory sweating, which is perspiration triggered by the anticipation, smell, or consumption of food. This hyperhidrosis is profuse and localized to the head, face, and neck, often occurring symmetrically. Gustatory sweating occurs because damaged autonomic nerve fibers that normally control salivary glands become misdirected and stimulate nearby sweat glands instead. This phenomenon indicates widespread autonomic neuropathy and is frequently seen in individuals with long-standing diabetes.
Sweating as a Hypoglycemia Indicator
In contrast to chronic changes caused by neuropathy, profuse, generalized sweating is an acute warning sign of dangerously low blood sugar, known as hypoglycemia. When blood glucose levels drop below approximately 70 mg/dL, the body recognizes this as a threat. This triggers a stress response designed to rapidly raise glucose levels.
As part of this protective mechanism, the adrenal glands release a surge of epinephrine (adrenaline) into the bloodstream. Adrenaline is a powerful hormone that causes a “fight-or-flight” reaction, and one of its immediate effects is the activation of sweat glands across the body. This perspiration is usually sudden, profuse, and generalized, often accompanied by other adrenergic symptoms like a rapid heart rate, shakiness, and anxiety.
Recognizing this pattern of generalized, clammy perspiration signals the need for immediate intervention to consume a fast-acting source of glucose. Hypoglycemia-related sweating can occur at any time, including during sleep, leading to night sweats that leave clothing and bedding damp. This acute sweating is distinct from chronic hyperhidrosis caused by nerve damage, as it results directly from the body’s hormonal response to low glucose.
Strategies for Managing Sweating Changes
Managing altered perspiration patterns requires different strategies depending on whether the problem is excessive or reduced sweating. For individuals experiencing hyperhidrosis in the upper body or gustatory sweating, topical treatments often provide relief. Clinical-strength or prescription antiperspirants containing high doses of aluminum chloride can effectively block sweat ducts in localized areas.
Managing Hyperhidrosis
In cases of severe or treatment-resistant localized hyperhidrosis, a healthcare professional may suggest medications such as oral anticholinergics, which block the chemical signals that stimulate sweat glands. For gustatory sweating, dietary adjustments are helpful, such as avoiding known triggers like spicy foods, caffeine, and alcohol. Injecting botulinum toxin (Botox) into affected areas, such as the face or armpits, is another option that temporarily blocks nerve signals to the sweat glands.
Managing Anhidrosis
For those dealing with anhidrosis, the focus shifts to safety measures since the body’s natural cooling mechanism is impaired. It is important to monitor body temperature carefully, especially during warm weather or physical activity, to prevent heat-related illnesses. Staying well-hydrated and wearing loose-fitting, breathable clothing helps the body regulate its temperature when it cannot rely on sweating. Avoiding prolonged exposure to high heat and recognizing early signs of heat exhaustion, such as dizziness or nausea, are necessary precautions.