If you have a HappyLight® Therapy Lamp model with a compact fluorescent bulb (CFL), it will get warm to the touch with prolonged use, so it is important to follow the instructions in the product manual about how to use it. Your HappyLight® Therapy Lamp should be treated like a regular lamp and should never be left on bedding or any other material that is not safe for lighting and electronics.
If you have an LED HappyLight model, it may get slightly warm as it is an electronic device but it will not generate the same level of heat as a normal CFL light bulb would.