Heliophobia is the unfounded and irrational fear and avoidance of sunlight (Milbry, 1911. A Pocket Medical Dictionary).
Common signs and symptoms include breathlessness, difficulty in thinking or speaking, dizziness, losing control and the inability to concentrate and palpitations, shaking, sweating and anxiety attacks.
It is treated through administration of Vitamin D supplements inasmuch as the person suffering from the disorder may have vitamin D deficiency. Behavioral therapy including exposure and fear reduction techniques may also be used to treat the disorder. Administration also of anti-depressant drugs may be used to early stages of the treatment.
Heliophobia, just like any other phobia, are psychological disorder. Fear of the sun may arise due to fear to skin cancer. Keratoconus or extreme optic sensitivity to sunlight and other bright lights may cause oversensitivity to sunlight.
It is diagnosed through examination of medical conditions and the reaction of the person to his unfounded fear of the sun.