Onsen - Risks

Risks

Although millions of Japanese bathe in onsen every year with few noticeable side effects, there are still contraindications to onsen usage, such as high blood pressure or heart disease.

In recent years, Legionella bacteria have been found sporadically in onsen with poor sanitation. Revelations of poor sanitary practices at some onsen have led to improved regulation by hot spring communities to maintain their reputation.

There have been reports of infectious disease found in hot bodies of water worldwide, such as:

• Various Naegleria species. While studies have found the presence of Naegleria in hot spring waters, the worrisome Naegleria fowleri amoeba has not been identified. Nevertheless, less than 5 cases have been seen historically in Japan, although not conclusively linked to onsen exposure.

Many onsen have posted notices for visitors, reminding anyone with open cuts, sores, or lesions to not bathe. Additionally, in recent years onsen are increasingly adding chlorine to their waters to prevent infection, although many onsen purists seek natural, unchlorinated onsen that instead does not recycle its water, cleaning baths daily. These precautions as well as proper onsen usage (i.e. not placing the head underwater, washing thoroughly before entering the bath) greatly reduces any overall risk to bathers.