Wudhu as a Precaution Against Sickness

Empirical and physiological experience are evidence for the fact that toxins within the human body continue to be expelled from the far limits of the body. These toxins settle on the hands, feet, face and head and appear in the form of various types of toxic pimples, boils and skin blemishes.

By washing the far ends of the body (the hands, face and feet) these toxins are flushed out. Either their toxicity is extinguished within the body, or the toxic substances are completely purged from the body.

(Al-Masaalihul Aqliyyah)