Heliosis refers to the medical condition that is caused by excessive exposure to the sun or sunlight. Some common synonyms for heliosis include photodermatitis, sunburn, sun rash, and solar dermatitis. Photodermatitis is often used to describe a more severe form of heliosis that results in blistering and swelling of the skin. Sun rash is used when referring to the red, itchy bumps that develop after sun exposure. Solar dermatitis is used to describe inflammation and irritation of the skin caused by exposure to UV radiation. No matter which synonym you use, it is essential to take precautions to protect your skin from the harmful effects of the sun.