AN "Allergy Formula" is a food that generally has a limited ingredient list, with only one animal protein source to help pinpoint an allergy or stay away from common ingredients. They tend to contain mild sources (such as chicken rather than beef) and are not rich. An allergy formula may or may not be grain free. They tend to be "simple" foods, so often times dogs that have a tough time stomaching rich foods willl do better on an allergy formula, despite not having allergies, just because of the short ingredient list and general mildness.
To me, the whole point of an"allergy" or "simple formula" is:
1) a shorter ingredient list to pinpoint allergies- I prefer california natural because they have higher meat content. Allergies or not, dogs are still carnivores.
2) a mild formula gentile on the stomach- again, cali nat is gentile, with more meat.
3) as low carb as possible, as carbs are not necessary and can cause problems if fed in excess
Some Allergy formulas I would recommend to someone having problems discovering the culprit of an allergy, or having sensitive tummy issues: California Natural formulas would be first pick, as they have more meat content than other "simple" formulas. Then maybe Wellness Simple Solutions, though it's really not impressive. From there, there's no other moderately acceptable limited ingredient formula. I will say that I do think that a home prepared diet of any kind is DEFINATELY most ideal for allergy dogs especially, these are just foods that I don't think are too bad, that I would recommend to someone entirely unwilling to do a home prepared diet.
Grain free formulas can work wonders for allergies- if grain are the problem, but if it's moreso a sensitive digestive system issue, then rich grain free foods CAN make it worse. Or, they CAN make it much better. Definately hit or miss. I've seen it go both ways.
a "grain free" formula is just that. They may be used for a dog with allergies if grains are the culprit of said allergy. Not all grain free formulas necessarily have more meat and less carbs. Some grain free foods are very rich, and that's why some dogs don't do well on them. Their portions are less than grain inclusive foods, and overfeeding can induce diarrhea or dark, sticky stools.
Natural Balance LID formulas do not meet what I would require from a grain free food.
To me, the point of going grain free is to
1) avoid allergies to grains- but there are far better options that meet this purpose.
2) to give a low carb diet- but LID is not low carb.
3) to give a diet higher in meat content- obviously with potato as the first ingredient, LID falls short in this department
4) to get closer to a species-appropriate diet- again, with the potato....
Some foods that I would recommend (based on ingredient list and meat/carbs): Orijen, EVO, (for now) Wilderness, and Instinct.