Hematidrosis, also known as hematohidrosis, is a very rare phenomenon in which the individual sweats blood, or blood-tinged sweat exudes from the skin. It is also called hematofolliculohidrosis because of the appearance of blood along with sweat from the openings of the sweat glands. This latter term was coined by Manonukul and his colleagues in 2008.
The pathophysiology of this unusual condition has been a mystery ever since it began to be described. The most commonly proffered explanation is that the capillary network surrounding the sweat glands become distended and rupture under conditions of extreme stress, allowing blood to enter the sweat glands. Hematidrosis then emerges along with the sweat from the sweat pores. This is quite often said to follow or coincide with the occurrence of extreme emotional or physical stress or exertion.
The other hypothetical causes of hematidrosis include systemic disease, vicarious menstruation (when blood oozes from other body surfaces than from the uterine endometrium as expected, at the usual time of a woman’s periods), psychogenic (in patients with trauma or stress, real or intensely feared), and the rare psychogenic purpura in which a woman develops hypersensitivity to her own red blood cells. As a result, she may develop red skin rashes resembling bruises, with bleeding from the stomach or intestines, and blood leakage into urine.
In many religiously inclined women in the past (though it is very uncommon now), the appearance of wounds, scars or bruises exuding blood without any self-inflicted or other lesion (called stigmata) was a mystery. Intense mental concentration on the sufferings of Christ, or similar ecstatic experiences, may be responsible for at least some of these cases.
The presence of neurotic symptoms has not been ruled out and appears to be elevated in this group of women. The characteristic stigma lesion consists of palpable bluish skin discolorations on the palm, preceding the actual oozing of blood which typically lasts for a long time.
Some identified causes include great fear: recorded cases include the fear of facing a storm while on board a ship, or the expectation of execution, as well as the fear of falling bombs during the German blitz of London, the fear of sexual assault or even chronic severe stress. Hysteria is a potent operator in some such situations, and these strong and intolerable emotional reactions may also cause psychosomatic illness leading to hematidrosis. It may even cause purpura as a result of causing sensitivity to one’s own blood. One woman used to experience bleeding from old scars when she experienced significant fear or anxiety.
The pathology behind this disorder was explained by Zugibe as follows: the rich capillary plexus around the sweat glands is intensely susceptible to stress, and this results in vasoconstriction. As a consequence the blood inside is trapped and the capillaries dilate until they rupture. This blood enters the sweat gland lumen and is eventually excreted as blood-stained sweat on the skin surface. Thus the appearance of blood in the sweat is the result of severe anxiety causing sympathetic overactivation to an extreme degree.
Another hypothesis put forward by Manonukul and others is that individuals who experience hematidrosis have stromal defects in the dermis which cause weakening of the skin support. The presence of lacunae predisposes to their communication with the dermal capillaries and leads to the formation of blood-filled spaces which dilate with the inflow or blood during times of stress. The blood drains from the sinuses into the canals leading into the sweat glands or straight on to the surface of the skin, which leads to bloody sweat.
The latter is dependent on the achievement of adequate pressure within these sinuses. Following the subsidence of the stimulus, the sinuses collapse leaving no trace. However, skin biopsies taken immediately after the occurrence of hematidrosis have sometimes shown signs of such traces. These are not blood vessels, as confirmed by immunoperoxidase studies. Other studies have failed to show such features.
Another study using biopsies in patients with hematidrosis showed obstructed capillaries with bleeding into the surrounding skin, but no evidence of anatomical abnormality. This led to the suggestion of an underlying vasculitis.