Determination of minimum erythema dose for narrow band UVB therapy and skin typing

Sir,

This letter is with regard to the article by Tejasvi et al. titled "Determination of minimal erythemal dose for narrow band-ultraviolet B radiation in north Indian patients: Comparison of visual and Dermaspectrometer ^® readings." ^[1] The authors do not mention whether the meter can detect erythema when the eye cannot detect it. This would be of significance with respect to the Indian skin.

With regard to the skin type III having a higher minimal erythema dose (MED) than type IV in some cases, we have observed the same finding while working with BB-UVB. ^[2] The MED seems to depend on sex and occupation of the patient. ^[2] Females have a lower MED, and similarly, men with indoor occupation have a lower MED, even if they are darker. ^[2] This finding underscores the requirement for separate skin typing for Indian skin. Because of this reason, the blind delivery of NB-UVB without MED assessment will lead to the delivery of either a very high dosage or grossly inadequate dosage of UV rays.

To overcome the problem of skin pigmentation by masking just perceptible erythema, it would be safer for the Indian skin to go down one step while ascertaining the MED, i.e., if MED has been determined using 750, 800, 850, 900, 1000mj and so on and just perceptible erythema is detected at say 900mj, then 850mj may be taken as the MED to calculate the dose of NB-UVB.