Yes and no. It is always best to use protection - such as a condom for a man or a dam for a girl. This is to avoid picking up STD'S (Sexually transmitted diseases). In the sense of "bad" as a general thought - then no. If you are practicing safe sex and the legal age (16 in the U.K), there is no bad consequence from oral sex. If you have been with your partner for a very long time - say 5 years plus. You can probably have oral sex without protection so long as you both go regularly for sexual health checks. But to reiterate - Oral sex isn't bad as long as you are using protection.