Your skin tends to become thinner as you age. Therefore, it is important to take care of your skin in order to keep it supple and thickened. Thinning of the skin may occur when the level of collagen in the skin decreases and skin elasticity is lost. Collagen is a protein found in the skin which helps to nourish the skin and make it healthy. Thin skin may also be caused by the long-term use of steroid ointments that cause the skin to bruise easily and become fragile and transparent. Luckily, there are a number of things you can try to make your skin thicker, stronger and firmer.