News related to dog allergies and dog nutrition

HEALTH CENTRE

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Sensitivities in pets

Sensitivities are where an animal responds to a material often in an inappropriate way. Many people are familiar with sensitivities either in themselves or their pets and often use the term, allergy to describe the reaction. However not all sensitivities are allergies for example many adult mammals including humans cannot easily digest the milk sugar lactose and the indigested sugar that enters the hind gut can lead to microflora changes that we notice in terms of loose stools and flatulence. Individuals behave differently to milk depending on their history and makeup and our pets are similar.

Allergies can be defined as sensitivities where the immune system responds to a particular material. The response is very specific and involves immunoglobulins of a type usually given the letter E (IgE) plus a battery of immune cell reactions. An allergen that causes an immune reaction may be from contact that is food-borne, through skin or the respiratory system eg food items, hay fever or allergies to insect bites. The allergic symptoms are usually a combination of intestinal problems seen as loose stools and / or skin problems seen as itchy dermatitis. It appears that the skin and gut have much in common in that they are the “outer barriers” of our bodies and the immune response to what the body considers to be an attack by an invader induces simultaneous symptoms in these areas.

What causes allergies? This is the question that has been asked by scientists for many years. It is believed that the body mistakes invasive proteins as being an attack by a disease causing entity. Many diseases induce normal immune responses that recognise the disease-causing entity eg bacteria, virus, fungi or animal parasite by their specific proteins. The protein is believed to have to be of a particular size ie bigger than about 16000Daltons, which means about 1000 x sugar molecules. In animal protein terms this is relatively large and during digestion most proteins are broken-down to much smaller peptides before absorption. So why has the body recognised these larger proteins? Possibly because of upsets in the intestines that have allowed some under-digested ingredients to cross into the blood or perhaps there are other, as yet unknown, factors at work.

Often Veterinary Surgeons will test for a food borne allergen by applying suspected allergen items to the skin and then looking for the tell tale local allergic response on the skin. Not unlike the rosette tests (known as Heaf or Mantoux) carried out in human medicine to indicate if a person has been exposed and will therefore react to TB exposure.

Some sensitivities and the more specific allergies can be resolved by simply removing contact with the item to which the animal is sensitive. This is the traditional approach of human and veterinary medicines i.e. avoid the food if you have a sensitivity to it. Human sufferers of food-borne allergies can often avoid eating the specific allergen e.g. egg, oranges, nuts or wheat.

Pet food makers have used the exclusion diet, which is a complete balanced pet food that clearly names its ingredients and avoids the more common sensitizers as a simple way of over-coming problems. It is surprising how often the use of exclusion diets have resolved problems before the causal material has even been identified. The exclusion petfoods have been referred to as “hypoallergenic” diets, which is a misnomer because they may cause allergic responses if the allergen is still present and theoretically all proteins can lead to an allergic response in susceptible individuals.

Graham Yeo, Pet Nutritionist

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