Most babies are able to begin sitting up when they reach the age of 4 months. However, some of them might need more time and start sitting independently when they become 7 months old. Until this time, the baby would definitely have learned how to roll and would be able to hold his head up too.
UV radiation, in the form of lasers, lamps, or a combination of these devices and topical medications that increase UV sensitivity, are sometimes used to treat patients with certain diseases who have not responded to other methods of therapy.
Hospital-based UV treatment uses only the specific part of the spectrum that is useful to treat skin conditions. This is not the case on a sunbed, where a much broader spectrum is used. Many sunbeds use mostly, or entirely, UVA light, which is ineffective for treating psoriasis without the added psoralen. Therefore, using sunbeds means taking on the risks of UV exposure, without much of the benefit to psoriasis.