UVC (100-290nm)

1. Germicidal
2. Blocked by ozone
3. Highest energy causing DNA damage (carcinogenic), potentially lethal

UVB (290-320nm)

1. Causes sunburn, skin cancer, photoaging, photosensitivity, vit D synthesis
2. Used for phototherapy in psoriasis & vitiligo (immunosuppressive)
3. Blocked by clear glass in home & car windows

UVA (320-400nm)

UVA2 (320-340)

UVA1 (340-400)

1. Causes immediate pigment darkening, drug photosensitivity, photo-allergy, photoaging, skin cancer, responsible for porphyria cutanea tarta
2. Used in PUVA for cutaneous T-cell lymphoma, psoriasis, alopecia totalis
3. Passes through clear glass

UV exposure

Latitude:   closer to equator = more direct UV exposure

Atmosphere conditions:  cloudy days may only reduce UV by 20%

Time of day:  sun is strongest btwn 10:00-4:00

Reflection:  80% of suns rays are reflected by surfaces: Snow, Sand, Water, pavement

Humidity:  wet stratum corneum transmits more UVB

Seasonal:  Maximal day is summer solstice=June 21^st  (minimum = Dec 21^st) 

Polymorphous Light Eruption

Actinic Prurigo

Actinic Prurigo II

Chronic Actinic Dermatitis

Lupus Erythematosus 

Psoriasis 

(Post-sunburn)

Photoonycholysis 

Rosacea

(sun sensitivity)

Urticarial Lesions