Can Houttuynia cordata be applied externally, and how is it used?

　　Houttuynia cordata is generally applied externally, with common methods including direct application of mashed fresh herb, wet compress with boiled liquid, application of powder mixed with water after drying, combined application with other herbs, and fumigation followed by topical application. Details are as follows:

　　1. Direct application of mashed herb: Wash fresh Houttuynia cordata, drain off excess water, crush it until juice is released, then apply directly onto the affected area. Cover and secure gently with clean gauze. This method is suitable for mild skin inflammation or insect bites.

　　2. Wet compress after boiling: Boil Houttuynia cordata with water, cool slightly, then soak clean gauze in the liquid, wring it until half-dry, and apply on the affected area for 15–20 minutes each time. It can be used to relieve skin redness or mild burns.

　　3. Application of dried powder mixed with water: Wash and dry Houttuynia cordata thoroughly, grind it into fine powder, mix an appropriate amount with water or honey to form a paste, and apply evenly onto the affected area. This is suitable for areas with minor skin damage.

　　4. Combined application with other herbs: Mix Houttuynia cordata with herbs such as dandelion and honeysuckle in appropriate proportions, boil with water until softened, mash, cool slightly, and apply onto the affected area. This can be used to relieve severe local inflammation.

　　5. Fumigation followed by topical application: Boil Houttuynia cordata with an appropriate amount of water. First, use the steam to fumigate the affected area while hot, then wait until the temperature is suitable before using gauze soaked in the liquid for wet compress. This is suitable for areas of joint or muscle discomfort.

　　Before applying Houttuynia cordata externally, ensure the skin has no obvious wounds or allergies. Monitor skin reactions during use. If symptoms such as increased redness, swelling, or itching occur after application, discontinue use immediately, wash the area thoroughly, and consult a healthcare professional if necessary.