This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
Excesses in sunbathing are usually quick to make themselves known. If headache, fatigue or upset stomach follow a sunbath, this indicates an overdose. Harm results from over-sunning just as it does from over-eating or any other form of excess.
Erythema (redness) and dermatitis (inflammation of the skin), both of which are painful and distressing, result from excessive exposure before pigmentation has occurred. Fever, headache, weariness, loss of appetite, languor, sleeplessness and such, result from too much exposure, or exposure to the hot mid-day sun. Such undesirable results prove the bath to have been carried to excess. Wherever possible, secure the sun-bath in the early morning or late afternoon, except during the cooler seasons of the year.
Burning and itching of the skin, erythema, aches and pains, and feelings of over-excitement or of depression and, sometimes insomnia result from over-stimulation and indicate that the bath should not be prolonged.
If any part of the body becomes burned or inflamed, due to too much exposure, wait until the burn is healed and the swelling gone before taking another sun-bath.
Sun-stroke is a very remote possibility. Heat-stroke may occur in weak individuals who stay too long in the sun when the weather is hot. If proper precautions are observed, this can never occur.
If, after a sun-bath, you should suffer from nose bleeding, congestion in the head, vertigo (dizziness), this is evidence that you took too strong a dose. In such a case, wait until you have fully recovered before taking another sun-bath and do not take so much next time.