If your dog is sensitive to something in his or her food, there is currently only one way to accurately identify which ingredient or ingredients are responsible and that's an elimination diet (or exclusion diet as it's sometimes called).
The process basically involves eliminating any potentially problematic ingredients from the diet until the symptoms of the sensitivity subside and then reintroducing them one by one to see which cause the problems to return. It can be time consuming and often frustrating but when done right the rewards are can be priceless.
Phase 1: Elimination
The first step of an elimination diet is to change on to a food that is as different to the current diet as possible. Make a note of the ingredients found in the food you are currently feeding as well as any treats or tidbits you regularly give your dog. Pay particular attention to any meats and grains as they are the most common offenders.
Once you have a comprehensive list of all of the ingredients your dog is currently eating regularly, it will be time to find a new diet that is, ideally, free from all of them.
As for what should be in the food (as opposed to what should not), diets based on ‘novel proteins’ can be a great help. These are proteins (usually meats) that your dog has never previously eaten and, therefore, has not had the opportunity to develop a sensitivity to. Which meats qualify as novel will vary from dog to dog but even for those that have experienced a wide range of meats in the past, there are still plenty of options including ostrich, hare, horse, kangaroo etc.
Generally speaking, simple diets with relatively few ingredients are often best at this stage as they provide less potential to cause problems.
With the enormous variety of commercial diets now on offer, you should be able to find something that fits the bill no matter how long your 'ingredients to avoid' list is. You can then use the ‘avoid ingredients’ filters on our Dog Food Directory to get a list of suitable candidiates.
Selecting the ‘clear labelling’ and ‘hypoallergenic’ filters will also help to rule out any foods that might have hidden nasties that could disrupt the elimination diet.
Hydrolysed proteins are proteins that have been chemically or enzymatically broken down into much smaller particles which are far less likely to cause problems. Many veterinary foods for sensitive dogs are made using hydrolysed proteins which can make them good options for this stage of the elimination diet.
Home-prepared diets, both cooked and raw, can work excellently for the purposes of an elimination diet as they give you total control over the ingredients. Care must be taken though to ensure the diet remains balanced as your dog could end up on it for a while. There are lots of good tips on home preparing food for your dog in the home cooking and raw feeding sections of the forum.
Treats and tidbits
To maximise the effectiveness of the elimination phase, dietary additions like treats and tidbits should not be given. You can always use some of the commercial or home-prepared food you decided on above but take care not to overfeed.
Even things like flavoured toothpastes should be avoided and only water should be offered to drink for the duration.
Making the change
Once you have decided on a suitable new diet, you can start to make a gradual change - take a look at our guide to changing diets for more information.
The effects of a dietary change tend to work their way from the inside out, so whereas some digestive changes can begin very quickly, the skin and coat can take much longer to respond. The full effects may take up to 12 weeks to come through so please be patient.
Some dogs may appear to get worse before they get better, especially when moving from a very inappropriate diet on to a high-grade food. This is known as a 'detox period' and common signs include increased moulting and/or dandruff and scurfy skin during the first week or two following the diet change.
Phase 2: Reintroduction
Once the symptoms of your dogs food sensitivity have completely subsided, you will be faced with a tough choice: stick with the current regime knowing that it is fine for your dog or start reintroducing ingredients one by one to properly identify which ones were the root cause.
If the elimination diet was nutritionally complete and high quality then there’s really no harm in sticking with it long term. Having said that, nutritional variety is enormously beneficial for dogs so consider very carefully introducing some variation now and then in the form of healthy, low risk dietary additions (novel meats, cooked veg etc).
If, on the other hand, the elimination diet was low grade (this would include many prescription diets) or nutritionally incomplete or if you would just like to get to the bottom of exactly what was causing the problem in the first place so that other beneficial ingredients aren’t avoided unnecessarily, then a careful programme of reintroduction is the way forward.
Naturally, this should be done very carefully and systematically. Select one of the ingredients from the list you made earlier and add a tiny amount to the daily diet. Provided everything is ok, you can gradually increase the dose but be sure to keep a very close eye out for any signs of problems reemerging. A loosening of the motions is usually the first sign but vomiting, itchiness, paw chewing, excessive wind or constipation are also common early signs that something is up.
If you notice any of these red flags, immediately remove the ingredient from the diet and record it as a food sensitivity for your dog.
In contrast, if you can feed a normal dose of the ingredient daily for a couple of weeks without any signs of problems returning you will know that your dog is not sensitive to it.
You can then move on to testing the next ingredient on the list. Each ingredient should be reintroduced individually to make sure the results are as reliable as possible.
Many dogs are sensitive to multiple ingredients so working through the list can take considerable time and patience but for dogs with a history of food sensitivities, it will be well worth it. Right now, this is the only way to get a true understanding of what foods your dog can and cannot tolerate which is vital information for any dog owner.