Shampoos will most likely exacerbate the dandruff problem by drying the skin further and removing essential oils from the coat ... so no shampooing. A better strategy is to add omega fish oil to your cat's diet. That can help with coat quality. There are lots of dietary pet supplements that contain omega fatty acids, but I just buy human grade fish oil gelcaps, puncture a hole in one end, and squeeze three drops of oil onto each of my cats' breakfast every morning.
I can't remember your cat's age or medical status, but dehydration (a common problem in cats with renal problems, diabetes, or hyperthyroidism) can cause major dandruff. Cats fed a kibble diet are also chronically dehydrated. The best way to deal with dehydration-related coat problems is to remove kibble from the diet and mix water into canned food to increase water intake.
Lastly, if the air in your home is dry, use a humidifier.
It's more than likely a symptom of his weight issue (not being able to groom properly) and poor diet. Getting him on a good canned food as we discussed on the other thread should help clear this up. Lack of hydration and animal fats can cause skin and coat problems.
Ah, yes. I didn't make the connection between the threads. Doodlebug is quite right. Obese cats often can't groom themselves effectively, and sometimes they just give up even trying. They lose spinal flexibility with all that extra fat in the way. Buy a nice soft infant hairbrush and give your cat a thorough brushing every day. That will help loosen and remove at least some of the dandruff while you're working on improving his diet, hydration, and weight.
Hi there! I can help with this also, from experience.. but the short answer is yes, the above posters are right. Go, Laurie and Doodle!
My cat Tequila (Mr. T) used to be just over 20 lbs. He had terrible dandruff, sensitive skin, and an inability to groom correctly. His previous owners were overfeeding him the sinful Science Diet dry. I was close to taking him to a pet dermatologist until I learned that it cost $125 just to see the guy.. no thank you! But I'm pretty sure it had to do with a combination of being overweight, and a possible slight grain allergy.
I transitioned him over to Avoderm canned - which is grain-free, and high in Omega-3's and essential oils. They make a dry formula too, but that obviously is not grain-free. You may want to try it. He eats one 3-oz can a day (1/2 morning, 1/2 night) and approximately a third of a cup of the dry during the course of the day. He is now down to about 15 lbs, his skin is dandruff-free, he can now groom himself (that's a biggie) and doesn't freak out (as much) when I brush him. His fur feels amazingly soft and supple, even other people say so. He's much happier and livelier.
Note there is some controversy about feeding cats avocado oil, as they're obligate carnivores, but I've had nothing but great things to say about Avoderm Canned.
Dandruff in cats is caused by oily skin, not by dryness. If you didn't wash your hair for 2-3 months, you would have dandruff - it is greasy, dead skin flaking off. If your cat is overweight and has cut back on his own grooming routine, you can also consider taking him to a groomer for a bath & blow dry - this will remove the grease, dead skin and excess dead hair.