1. When the essential oil is applied to the skin, it will volatilize, take away the heat on the skin surface and make the skin feel hot; 2. Most of the essential oils are doped with drugs such as ginger, which will cause fever after application; 3. Most of the effective components in essential oil have the effects of warming meridians and activating blood circulation, warming kidney and helping yang, and are used to improve the symptoms of joint swelling and pain or kidney deficiency, backache and cold pain, so as to stimulate the yang in the body to warm outside, and it is normal to have a fever.