They are not very common, but can be considered as a possible cause of unexplained itching. Ball mites are actually quite small animals that are only 0.2 mm long. The fertilized females may, however, swell and become spherical with a diameter of up to 2 mm.
One of the water mite species is called Pyemotes ventricosus. It lives as a parasite on the skin of moth larvae and beetle larvae. In places where there are many larvae, there can be an excess of hungry water mites. This could be in old hay, or in granaries and other places where there are many insect larvae. Another water mite species live on the deathwatch beetles.
Water mites crawl around in search of a larva, or they move passively through the air with dust. If they end up on a person, they will hang on and try to inject their digestive enzymes into the skin. This results in an itchy, allergic skin reaction, similar to that of fur mite bites. They typically bite the hands, arms and chest. There are known examples of people being exposed to water mites in their workplace who brings them home in the clothes and has infects the rest of the family.
Water mites cannot survive without insect larvae for long periods of time and if they end up on a human they will die after a short period of time. When their mouthparts are injected into the skin, they do not stick very well to the host. A shower will wash them off.
When the water mites have been confirmed by microscopy, control measures should be taken. This is done by combating their host animals – the insect larvae.