Just some questions to narrow down the possible causes of your rat's hair loss and scabs.

1. What are you feeding?
A diet too high in protein and fat can cause itching and scabbing around the neck and shoulders. Also a diet deficient in the essential fatty acids will give the same results-- scabs. If you are feeding a seed mix-- cut way back-- a balanced diet like rodent block, fresh fruits and vegetables, plenty of water and perhaps a vitamin supplement or better yet, a coat and skin conditioner for pets (pet shops sell a good one for ferrets-- but it smells like fish) would be your best bet.

2. What type of bedding are you using?
Sometimes hair loss, scabs and itching can be due to allergies or contact dermatitis. Cedar and pine are not good bedding materials-- may people use CareFRESH, a recycled paper product. There are other choices that are recommended in the Rat FAQs. However, allergies could be due to many items-- (sometimes food allergies-- although these are not common).

3. Hair loss can also be caused from scratching at external parasites like mites, lice or fleas. Mange is also a possibility-- also caused by a parasite. Burrowing mites cannot always be detected by a skin scraping. You may need to dose with the Ivermectin. Generally, 3 doses separated by a week is recommended. The following is the location of the RMCA Drug Chart--look in the list-- Ivermectin is listed-- dose and treatment.
<https://www.rmca.org/Articles/dchart.htm>
Ivermectin can be purchased at a feed store for livestock-- brand name Equimectrin-- it is a horse wormer. Using a portion as big as a grain of rice to rats as recommended above is very safe and effective.

4. Another possibility is a fungal infection like ring worm which is common in guinea pigs-- it looks like a bald patch with dry scaly skin.

5. The last and hopefully not the cause of hair loss can be caused by auto-immune problems like Cushings Disease: <http://www.io.com/~lolawson/cushings/>

"Anipryl is the only drug licensed for use in dogs that suffer from Cushing's disease, a neurodegenerative hormonal disorder of the pituitary gland and hypothalamus in the brain. Dogs with Cushing's disease have decreased hypothalamic dopamine levels and Anipryl works to restore the natural balance of important brain chemicals, especially dopamine, which in turn helps to alleviate the clinical signs of Cushing's disease."

Quoted from:
PETS Magazine November/December 2001
Cushing's Disease & CCD, pg 11
<http://www.pets-magazine.com>

(We haven't tried this with rats, but it would probably be worth asking a vet about!)

Treat with for the most common causes and eliminate the easy problems first. Let rat-help know if this continues to be a problem. It can be very upsetting to see our beloved pets looking so miserable.