Normally a full complement of body protection is worn especially if you are racing with ATVs. A set of ATV gear should include a helmet, goggles, body suit, gloves and boots. And since racing with ATVs is done in rough terrain, and most of these terrains are treacherous especially if you are not careful, it would never hurt to have every bit of protection you can get. Even loose earth flying around can get to an unprotected eye and blind you if you are not wary enough.
Your helmet is the most important safety ATV gear, not only in ATV but in other sports as well since the helmet prevents fatal head injuries. It is imperative too that the helmets used should at least be designed for ATV use since it would include a proper face protection. These face protectors aside from protection against vehicle crashes can also protect your face from flying debris, which is bound to happen a lot especially if you are racing with ATVs.