Recent news suggests that dyeing hair using dark dyes can - over the course of over a decade or more, increases the risk of developing certain types of cancer. Then again, so does everything up to and including barbecued food and fresh vegetables. Personlly, I would rather live a richer but shorter life than follow the advice of the cancer scaremongers a live off distilled water and tofu (made from GM free soya crops, of course)
Yes it can be..... Always be sure to do a skin test before using a hair dye and don't dye your hair until 48 hours later. It's important as my friend dyed her hair and had a severe allergic reaction! Head swelled, eyes puffed out! Hospitalised for a week!..... so if you dye your hair, read the instructions, do the skin test and definitely don't apply the dye for at least 48 hours!