I have read that the Vaseline keeps moisture off of the skin and that is how it protects it from freezing. It makes sense to me. I am sure it is not the one and only cure all frostbite answer though. I have put it on my chickens and I am not sure it has helped but we will see.
Frostbitten comb HELP!!!!!!!!!! - Page 4
Right now it sounds like only a very small part of the comb is actually frostbitten. Those tips of his comb which have turned white will eventually turn black and fall off, leaving behind a scab. Eventually the comb will completely heal up.
To prevent further frostbite, simply apply vaseline like another poster mentioned. When applying the vaseline, it also helps to massage any purple areas to encourage blood flow. Be careful not to massage the white or black ares though, as touching that too much may be painful for your bird.
Keep an eye on the rooster to be sure he doesn't develop any infection and acts normally. (Eats, drinks, and is active) Some roosters are just more prone to frost bite. Typically, after the first winter a rooster will no longer develop frostbite on his comb or wattles.
Welcome to BYC Puffy. Vaseline won't really keep your rooster's comb from getting frostbite. It just sometimes happens sometimes. High humidity combined, or the comb getting wet with freezing temperatures are the cause. You may not know the full extent of the damage for a few days. Sometimes it looks better after a couple of days. You can apply some iodine or plain Nesosporin ointment, but be gentle since the comb will be painful and may bleed. If the tips were frozen, they will most likely become rounded, and that really isn't too serious. Make sure the coop is dry, no wet spots, and has some overhead cross ventilation. Pictures are welcome.