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For a person to flush is to become markedly red in the face and often other areas of the skin, from various physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is milder, generally restricted to the face, cheeks or ears, and generally assumed to reflect embarrassment. Flushing is also a cardinal symptom of carcinoid syndrome—the syndrome that results from hormones (often serotonin or histamine) being secreted into systemic circulation.

Causes of flushing [link]

• Alcohol flush reaction
• An abrupt cessation of physical exertion (resulting in heart output in excess of current muscular need for blood flow)
• Emotions: anger, embarrassment (for this reason it is also called erythema pudoris, from Latin "redness of embarrassment")
• Sexual arousal, especially orgasm, (see section to follow)
• Inflammation (for example, caused by allergic reaction or infection)
• High doses of non flush free niacin (vitamin B₃)
• Caffeine consumption
• Sexual intercourse (see below)
• Some recreational drugs, such as alcohol, heroin, cocaine and amphetamines
• Carcinoid tumor
• Mastocytosis
• Chronic obstructive pulmonary disease, especially emphysema (also known as "pink puffer")
• Mixing an antibiotic with alcohol
• Rosacea
• Histamines
• Spicy foods
• Powerful vasodilators, such as dihydropyridine calcium channel blockers
• Herxheimer reaction (caused by antibiotics)
• Iron poisoning^{[citation needed]}
• Reactive hypoglycemia
• Atropine poisoning
• keratosis pilaris rubra faceii
• Carbon monoxide poisoning
• Antiestrogens such as Tamoxifen
• Hyperstimulation of the parasympathetic nervous system, especially the vagus nerve
• ACNES Abdominal Cutaneous Nerve Entrapment Syndrome, usually in patients who have had abdominal surgery
• Compression of the nerve by the sixth thoracic vertebrae
• Butorphanol reaction with some narcotic analgesics (since butorphanol is also an antagonist)
• Sunburn (erythema)
• Polycythemia Vera
• Vinpocetine
• Body contact with warm or hot water (hot tub, bath, shower)

This list is incomplete; you can help by expanding it.

Sex flush [link]

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. The sex flush tends to occur more often under warmer conditions and may not appear at all under cooler temperatures.

During the female sex flush, pinkish spots develop under the breasts, then spread to the breasts, torso, face, hands, soles of the feet, and possibly over the entire body. Vasocongestion is also responsible for the darkening of the clitoris and the walls of the vagina during sexual arousal. 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.

The sex flush typically disappears soon after orgasm occurs, but this may take up to two hours or so, and sometimes intense sweating will occur simultaneously.

See also [link]

• Pallor
• Erythema
• Rash
• Cholinergic urticaria