Deca is one of the more mild steroids when it comes to hair loss. The worst steroids for your hair line are primo, EQ, masteron and winstrol.
I have researched hair loss from steroids extensively. Using any steroid will speed up hair loss. It's inevitable. How much it speeds it up and how fast you loose your hair is dosage dependant and largely based on your genetics.
The best thing you can do for hair loss prevention is:
1. supplement with finasteride at 1mg/day
2. Daily use of a 2% nizoral shampoo
3. Daily use of a rogaine (minoxidil) spray
The N2shampoo from N2BM.com absolutely TRIUMPHS the 2% nizoral shampoo. I can't wait for it to be back in stock. N2BM.com said by the new year it should be available for sale.
hairloss is intensified from DHT derivative compounds. also ALL HORMONES convert to DHT. Deca meanwhile is unique, its not a DHT at all, its actually a DDA. this means it swamps DHT in the body so its not a factor. this is great because it means you can run lots of deca without worrying about hairloss! the downside however is DHT is our sex hormone, so when you swamp it in the body you can expect problems in the dick department.
Deca on its own is quite safe for your hair, but the other steroids in the stack might not be as safe. If you are taking deca alone, I would rather be concerned with other issues.