The sex flush is a common, involuntary physiological response characterized by the temporary reddening or darkening of the skin during sexual arousal. This visible change is a manifestation of the body’s preparation for sexual activity and is a normal part of the human sexual response. Though it often goes unnoticed, the presence of this flush indicates an increase in systemic blood flow triggered by heightened excitement.
Appearance and Characteristics
The visual appearance of the sex flush is typically macular, presenting as a flat, blotchy pattern that can resemble a mild rash. The color ranges from a light pink hue in individuals with lighter skin tones to a deeper red or purplish pigmentation in others. Individuals with olive or darker complexions may notice a subtle darkening of the skin rather than a distinct red mark, making the phenomenon less obvious.
The flush usually first appears across the upper abdomen and spreads quickly to the chest, neck, and face. The coloration can extend further to the back, shoulders, and occasionally the extremities. This physical sign is highly variable, differing greatly in its intensity and the total area of the body it covers from person to person and from one instance to the next.
The Physiological Mechanism
The underlying reason for the sex flush is vasocongestion, which involves the engorgement of tissues with blood. During sexual arousal, the body involuntarily redirects a greater volume of blood toward the skin’s surface, particularly to the peripheral capillaries. The dilation of these small blood vessels near the surface of the skin allows more blood to flow through, creating the visible effect of redness or flushing.
This sudden increase in surface blood flow is an involuntary action controlled by the autonomic nervous system. The parasympathetic division of this system becomes highly active, moving the body into sexual readiness. The resulting vascular dilation in the skin is part of the same systemic response that causes blood to engorge the erectile tissues in the genitals, preparing the body for orgasm.
Timing within the Sexual Response Cycle
The sex flush occurs within the four-stage human sexual response cycle, a model developed by researchers Masters and Johnson. While vasocongestion begins early in the Excitement phase, the skin flush typically becomes most pronounced during the Plateau phase of arousal. The Plateau stage is characterized by a sustained and intensified level of physical excitement just before orgasm.
The flush reaches its peak intensity just before or during orgasm. Following the culmination of sexual tension, the flush begins to fade quickly during the Resolution phase as the body returns to its pre-arousal state. Not everyone experiences this phenomenon; studies indicate it occurs in approximately 50 to 75 percent of females and around 25 percent of males.