Flushing is to become markedly red in the face and often other areas of the skin, from various physiological conditions. Flushing is generally distinguished from blushing, since blushing is psychological, milder, generally restricted to the face, cheeks or ears, and generally assumed to reflect emotional stress, such as embarrassment, anger, or romantic stimulation. Flushing is also a cardinal symptom of carcinoid syndrome—the syndrome that results from hormones (often serotonin or histamine) being secreted into systemic circulation.
abrupt cessation of physical exertion (resulting in heart output in excess of current muscular need for blood flow)
abdominal cutaneous nerve entrapment syndrome (ACNES), usually in patients who have had abdominal surgery
alcohol flush reaction
antiestrogens such as tamoxifen
atropine poisoning
body contact with warm or hot water (hot tub, bath, shower)
butorphanol reaction with some narcotic analgesics (since butorphanol is also an antagonist)
caffeine consumption
carbon monoxide poisoning
carcinoid tumor
chronic obstructive pulmonary disease (COPD), especially emphysema (also known as "pink puffer")
cluster headache attack or headache
compression of the nerve by the sixth thoracic vertebrae
coughing, particularly severe coughing fits
Cushing's syndrome
dehydration
dysautonomia
emotions: anger, embarrassment (for this reason it is also called erythema pudoris, from the Latinized Greek word for "redness" and the Latin "of embarrassment")
fever
fibromyalgia
histamines
homocystinuria (flushing across the cheeks)
Horner's syndrome
hot flush
hyperglycaemia
hyperstimulation of the parasympathetic nervous system, especially the vagus nerve
hyperthyroidism
inflammation (for example, caused by allergic reaction or infection)
iron poisoning
Jarisch-Herxheimer reaction (caused by antibiotics)
keratosis pilaris rubra faceii
Kratom
mastocytosis
medullary thyroid cancer
mixing an antibiotic with alcohol
neuroendocrine tumors
niacin (vitamin B3)
pheochromocytoma
polycythemia vera
powerful vasodilators, such as dihydropyridine calcium channel blockers
severe pain
sexual arousal, especially orgasm (see following section)
sexual intercourse (see below)
sneezing (red nose)
some recreational drugs, such as alcohol, heroin, cocaine and amphetamines
spicy foods
sunburn (erythema)
tachycardia
vinpocetine
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.