My mother in law always sees ants crawling everywhere but they do not exist. Any advice?

Have there been any medication changes?

Bongbong, sounds like your Mom-in-law as an Urinary Tract Infection.

Take her to see her primary doctor who will give her a test [pee in a cup]. If it comes back positive, the doctor will prescribe antibiotics.

My Dad had the same thing happen to him. He was seeing ants on the wall and in his food. Sure enough it was a UTI. Once the antibiotics started to kick in, less and less ants were being seen, eventually they all went away.

UTI's can cause all types of difference things in elders. Even mimic dementia.

My mother has macular degeneration which caused her to see it 'raining' all the time when it wasn't. When I took her to the opthamologist, she was diagnosed with macular degeneration, and he said all sorts of vision issues CAN come from this disease, and that she needed corrective glasses. Now that she has them, she doesn't see it raining anymore. Has your mother's eyes been checked for macular degeneration?

Your profile says your mother has vision problems but doesn't mention any kind of cognitive impairment. I don't know of any eye disease that causes a person to see ants that are not there. It sound more like a visual hallucination to me. Pops sees lots of things that aren't there. To him it's real, we play along but he has severe cognitive impairment caused by a brain injury so that's why he does it.