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After lots more googling over the last couple months, I’ve hit on a new hypothesis about my itching: it might be caused by Cheyletiella blakei, a mite that lives and breeds on cats but is “highly mobile” and occasionally causes intense itching in nearby humans.
Some facts in favor of C. blakei:
- The most easily visible sign of the mite is “walking dandruff” along the back of the cat, especially in the lumbrosacral region. (I think the dandruff is skin flakes being carried by the mites, which are almost impossible to see, but one or two sources say that the walking dandruff is the mites.) My cat Shedubi has dandruff mostly along her back, concentrated at the lumbosacral region.
- If I put my hand or face near some cloth where Shedubi has been sleeping, I feel the itching almost immediately. This is another common sign of Cheyletiella.
- Cheyletiella is most active at night and the itch it produces often feels like a “crawling sensation”. That’s how it’s been for me. Often the itch feels to me like grains of cornmeal on my skin.
- In my diary, I found that I had brought Shedubi to a veterinary clinic for the first time on July 5, and on July 7, I had itching so intense that it “shut me down”. I had itching before this, but it was not nearly this intense, and Zyrtec usually shut it down. Sometime after this (I have no exact record), the itch became most intense at night (starting almost exactly at 12:00 a.m. standard time) and neither Zyrtec nor any other antihistamine had any effect on it (suggesting that the itch is not an allergic reaction). Before July 5, there is just one note, on June 26, about feeling itchy and being annoyed by cat-hairs. Also, before July 5, I don’t have any record or memory of proximity to Shedubi causing me to itch (I first got her in July of the previous year). I did record that she was itching a lot before then, though; that’s partly why I brought her to the vet. Bottom line, it sounds like Shedubi may have picked up some mites while at the clinic, though it’s not completely certain.
- Shedubi sneezes and itches, though not a whole lot. When she sneezes or scratches herself, usually I am feeling especially itchy right at the same time.
Some facts against C. blakei:
- I haven’t seen any of the dandruff flakes on Shedubi’s back move. I’ve stared at black specks of dirt on my skin, where I had this itch and where I thought I saw the speck move, but I never saw a speck move while I was looking at it carefully (watching to see if its distance from something nearby changed).
- Normally, when a person suffers from C. blakei, they get little red skin lesions. I don’t have the characteristic red skin lesions. However, I read in one place that sometimes people get “pruritus without lesions” (that’s what I’ve had), and actually, I think I did have a few lesions on my scalp, or at least some really bad eczema. Also, the literature says that even though the person’s face typically itches and they have an urge to rub their face, no lesions appear on the face. That’s exactly what’s been happening.
- My main symptom is actually not itching, it’s this weird “wound up” feeling. (Does anyone know a medical term for feeling so wound up, you can’t slow down or focus on anything for more than a couple seconds?) The itch is always accompanied by the wound-up feeling, but the wound-up feeling is usually not accompanied by the itch. I’ve had the wound-up feeling most of the time I’ve been in Indiana, including the two years before I got Shedubi. It has subsided within 48 hours each time I have gone out of town.
Some other facts of interest:
- The mite is highly contagious, but most cats and most people don’t have symptoms. My other three cats don’t itch, sneeze, or have dandruff.
- The mite cannot reproduce on people; it needs a cat for a host. Without a proper host, Cheyletiella mites usually die off within two days, ten days at most.
- Nobody knows how the mite causes itching or lesions in humans. The presumption is that the lesions are from bites, but no one’s caught a mite in the act.
- The mite is extremely difficult to see with the naked eye even though it’s about 1/3 of a millimeter long (big enough to resolve with the naked eye). They’re rather translucent and, I think, they tend to blend in against most backgrounds.
- I’ve only come across one documented case of a C. blakei mite being found on a human. Usually veterinarians can find some of the mites by scraping the skin on the cat’s back and putting the mites in alchohol, but I’ve repeatedly seen articles say, “But we were unable to recover any mites from the person.” The presumption is that the mites are “highly mobile” and are long gone by the time you start looking carefully for one that has caused an itch.
- Most doctors don’t know about Cheyletiella mites, which also have zoönotic species that infest dogs and rabbits. The literature says they’re probably much more common than reported, due to the difficulties of identifying them or even suspecting them. Most people suffering from them do not suspect that the itch is coming from a pet. They consult an ordinary people-doctor or dermatologist, who of course can’t figure it out. And when I told my vet that it seemed to me that Shedubi was making me itch, she didn’t want to get involved with trying to diagnose and treat a person.
Shedubi and I have an appointment at the veterinary clinic tomorrow morning. I told them that I’d like them to check for C. blakei, and they said they’d try. I’m going to print out some of the journal articles I’ve found and summarize the main facts as above. I hope I don’t appear to be a crackpot. Or rather, I hope I get to talk with a veterinarian who enjoys solving an unfamiliar mystery (or one who already knows all about Cheyletiella).
