Flushing is also a cardinal symptom of carcinoid syndrome—the syndrome that results from hormones (often serotonin or histamine) being secreted into systemic circulation.

Commonly referred to as the sex flush, vasocongestion (increased blood flow) of the skin can occur during all four phases of the human sexual response cycle.

Studies show that the sex flush occurs in approximately 50–75% of females and 25% of males, yet not consistently.

During the male sex flush, the coloration of the skin develops less consistently than in the female, but typically starts with the epigastrium (upper abdomen), spreads across the chest, then continues to the neck, face, forehead, back, and sometimes, shoulders and forearms.

[citation needed] The sex flush typically disappears soon after reaching orgasm, but in other cases, may take up to two hours or more, and sometimes intense sweating occurs simultaneously.