Skin will continue to burn until cold water or ice is applied, so always cool down the burn first. Ice is good for
most burns, but severe burns can only tolerate cold water.
Be wary of Sunburn sprays and creams from the drugstore - some of these contain lanolin, which actually causes increased pain once the cool cream or spray is warmed by the heat of your body. Aloe vera products are often just lanolin with a touch of aloe added, so caution should be taken before using these. Even pure aloe will not prevent peeling later.
Lavender Essential Oil is a miraculous, natural cure for sunburn, after cooling down the burn with tea (see below). You want to be careful getting the oil onto the burn because simply touching the burn will hurt. It is best to drip it on, then spread it (using very gentle pressure) with a piece of tissue. After about a half hour or less, the pain should be gone. The pain should not return unless you jump in the shower soon after application of the oil. You may need to reapply the oil in the morning. That's it. No more pain, no blistering, AND you get to keep the color. Even those of us who are pale as ghosts won't peel.
Make a pot of boiling water and steep many tea bags to a very strong tea in a large pot. Add ice until the tea is just slightly warm. Put a bath towel (preferably a brown one, as a white one will probably be "dyed" brown) into the pot and keep turning the towel until it has soaked up all of the tea. Have the sunburned person lie on the floor or bed on top of an old towel to catch drips. Place the wet towel over the sunburned area of the body. Leave the towel on for a half hour for a moderate burn and an hour for a strong burn. The slightly warm tea will actually feel very cool on burned skin, and cold water would be almost painfully too cold on the hot skin. The burned person immediately feels relief from the wet, getting cooler and cooler gradually, with the actual temperature of the skin also cooling.
If the sunburn is not localized to one area, you may want to soak in the tub instead. First, clean the tub with hydrogen peroxide or a small amount of bleach - and be sure to rinse the tub thoroughly. For this bath you will need tons of tea bags. Brew the tea with boiling water until it is very strong, and you can cool this down with half cold water. You should not get in until the water is no longer warm, and be sure to get out when the tea water gets too cold. You will need to either lie down in the tub or have the tub filled high enough to cover all the sunburned areas.
The tannic acid in the tea draws the burn out of the skin and heals it. After just one application, most sunburns are no longer painful and are much less red. However, this treatment will act on the pain but may not prevent peeling.