Night sweats: why do we sweat at night?

In many cases, sweating at night is a normal physiological response.

As during the daytime, the body continues to regulate its internal temperature in order to remain within a temperature range in which it does not need to mobilise major mechanisms for heat production or heat loss. If this range is exceeded, even slightly, the sweat glands may be activated. Several factors can cause this rise in temperature during sleep. A bedroom that is too warm, thick or poorly breathable bedding, or unsuitable nightwear can all increase body heat and therefore lead to night-time sweating.

Reminder : Sweat primarily serves to dissipate heat and to maintain the body at a temperature of around 37°C.

Let us also note that thermal regulation varies over the course of sleep cycles. During certain phases, particularly rapid eye movement (REM) sleep, the body’s ability to adjust its temperature is reduced. This can promote more pronounced sweating, even in the absence of heat.

Beyond environmental factors, certain lifestyle habits can encourage sweating during the night. Diet, in particular, plays an important role. Heavy meals, spicy foods, alcohol or indeed caffeine can increase thermogenesis, that is to say the production of heat by the body. This rise in temperature can persist during the night and trigger sweating. Tobacco is also associated with increased perspiration. It stimulates the body to produce adrenaline, a hormone that raises body temperature.

Night-time perspiration may also have an emotional origin and be linked to activation of the autonomic nervous system, independently of any increase in body temperature. Stress, or even simply nightmares, can trigger night sweats. These may also be associated with sleep disorders, such as sleep apnoea, which is characterised by repeated interruptions in breathing during the night, leading to activation of the nervous system and a stress response in the body. Restless legs syndrome can also fragment sleep and promote sweating.

Night sweats tend to become more frequent with age, particularly in women, due to hormonal fluctuations.

Indeed, night sweats are one of the common discomforts brought about by the menopause. The reduction in oestrogen disrupts temperature regulation by lowering the threshold at which sweating is triggered. Even minimal temperature variations can then be enough to induce hot flushes, often during the night. It should be noted that in men, a decrease in testosterone may also be accompanied by similar symptoms, although this is less common.

Certain medical conditions and medications can also cause night sweats.

Hyperthyroidism, for example, increases the basal metabolic rate, leading to greater heat production and therefore increased sweating, including at night. Similarly, in people with diabetes, episodes of nocturnal hypoglycaemia can activate the sympathetic nervous system and trigger profuse sweating. Gastro-oesophageal reflux disease (GORD) is sometimes mentioned. Although this association is not consistently found in studies, some clinical observations suggest that episodes of nocturnal reflux, accompanied by discomfort or pain, may trigger sweating. Antidepressants or certain oral contraceptive pills also appear to be associated with night sweats, but there are still relatively few studies on this topic.

In some cases, night sweats may be associated with more serious medical conditions, although this remains relatively rare. Certain infections (tuberculosis, HIV, glandular fever, endocarditis) may be accompanied by fever and night sweats. Haematological diseases, such as lymphomas or leukaemias, are also associated with night sweats, often accompanied by other symptoms such as unintentional weight loss, fatigue or persistent fever. It is, however, important to emphasise that, in the majority of cases, night sweats are not related to a serious illness.

A medical consultation is nevertheless recommended if night sweats are severe, persistent or unusual, or if they are accompanied by other symptoms. Otherwise, adjusting one’s lifestyle habits is often sufficient to improve them.

Several approaches can help to address night-time sweating. In most cases, a few easy changes can help to reduce night sweats. First of all, it is important to monitor the temperature of the bedroom, which should ideally be between 18 and 19°C. In the same way, bedding and nightwear should not trap heat and moisture. This is why it is generally recommended to use cotton or linen rather than synthetic fabrics.

Certain evening habits can also be adjusted. Hearty meals, alcohol, very hot drinks or spicy foods increase the body’s heat production and may trigger night sweats. It is therefore preferable to limit them in the evening. Finally, stress and emotions before bedtime can activate the sympathetic nervous system: establishing a calming routine (reading, breathing exercises, meditation) may help to reduce these episodes.

If night sweats are due to the menopause and are poorly tolerated, the doctor may prescribe hormone therapy. The aim is to stabilise hormone production and thus prevent hot flushes and the associated sweating. Similarly, in cases of hyperthyroidism, treatments designed to regulate the production of thyroid hormones can help reduce excessive sweating.

While homeopathy may also help in cases of night sweats, it is preferable to seek advice from a healthcare professional before beginning a course of treatment.

Certain plants or food supplements have indeed shown beneficial effects in cases of night sweats. A study conducted between 2018 and 2019 with 163 postmenopausal women evaluated the effect of evening primrose oil (1,000 mg, twice daily for 8 weeks) on hot flushes and night sweats. Although no significant improvement was observed with respect to hot flushes, the results did show a significant reduction in the frequency and severity of night sweats in the treatment group compared with the placebo group. These findings suggest a potential effect, although the mechanisms of action remain poorly understood and the clinical data are still limited.

• MCCARTHY L. & al. Night sweats: A systematic review of the literature. The Journal of the American Board of Family Medicine (2012).

• BRYCE C. Persistent night sweats: Diagnostic evaluation. American Family Physician (2020).

• OSHVANDI K. & al. The effect of evening primrose oil capsule on hot flashes and night sweats in postmenopausal women: A single-blind randomized controlled trial. Journal of Menopausal Medicine (2021).

• JOFFE H. & al. Sleep and menopause. Menopause (2025).