Solar Index and Skin Type

Risk of damage to skin

Solar index	Skin type
	Burns in the sun, may tan (Category 1)	Tans with little or no burning (Category 2)	Naturally pigmented skin - brown (Category 3)	Naturally pigmented skin - black (Category 4)
1	low	-	-	-
2	low	-	-	-
3	medium	low	-	-
4	medium	low	-	-
5	high	medium	low	-
6	high	medium	medium	low
7	very high	high	medium	medium
8	very high	high	medium	medium
9	very high	high	medium	medium
10	very high	high	high	medium

Notes

The solar index does not exceed 8 in the UK (8 is rare; 7 may occur on exceptional days, mostly in the two weeks around the summer solstice).

Indices of 9 and 10 are common in the Mediterranean area.

Assumptions

Category	People covered	Approximate MED 1
Category 1: 'burners'	most UK indigenous groups	< 300 J m -2 effective
Category 2: 'tanners'	mostly UK non-indigenous and non-naturally pigmented groups	600 J m -2 effective
Category 3: 'naturally brown'	mostly Asian and middle and south American groups	800 J m -2 effective
Category 4: 'naturally black'	African and Caribbean groups	1000 J m -2 effective

1 Minimum Erythemal Dose. One MED is the dose required to produce a minimum redness on sun-sensitive skin. Each value given in each of the categories represents an approximate mid-point value for a range. In the monthly solar reports the sensitive group appropriate to Category 1 is used with a MED of 200 J m ^-2 effective.

One MED equals two SED (Standard Erythemal Dose), which is described in the International Commission on Illumination Technical Report Standard Erythema Dose, a Review, CIE 125-97.

Risk level	Effect
low	redness (erythema) in 2 hours or more (11:00-15:00 GMT in a UK summer
medium	redness (erythema) in between 1 and 2 hours
high	redness (erythema) in between 30 minutes and 1 hour
very high	redness (erythema) in less than 30 minutes

Last reviewed: 18 December 2008