Nauseous Crawlers are yellow variants of regular Crawlers. Any players that linger too long in front of one will be sprayed with a yellow fluid that will hold them in place for a few seconds, thus stunning them. This is hinted by the crawler stopping in one spot, and it will begin to puff up slightly and shake, before releasing the fluid. This attack is not blocked by effects such as which would otherwise negate the stun effect.
- After Update 10.0 (2013-09-13), crawlers will now crawl towards players at a very fast pace, almost as fast as the other infested, and the lower half of their bodies have been removed. New animations for the spraying of fluid and attack animations have also been added.
- Nauseous Crawlers are a relatively rare spawn, seen only in small numbers of 3-6 in most missions when spawning by themselves. However, Mutalist Ospreys can spawn them frequently as carried passengers.