Allergy to Tree Nuts & Sesame

Allergy to peanuts and tree nuts is the leading cause of fatal and near fatal reactions to foods.

Tree nuts encompass a group of foods that commonly include walnut, almond, hazelnut, cashew, pistachio, and Brazil nuts. Like peanut allergy, patients allergic to tree nuts usually do not outgrow or lose their sensitivity during their lifetime.

Tree nuts are being added to an increasing variety of foods such as barbecue sauces, cereals, crackers, and frozen desserts. Ethnic foods, commercially prepared baked goods, and candy can be cross contaminated with nuts as they are frequently being used in some varieties of foods.

These foods indicate the presence of Tree Nuts:

  • Almonds
  • Brazil nut
  • Cashew
  • Chestnut
  • Filbert/hazelnut
  • Hickory nut
  • Macadamia nut
  • Marzipan/almond paste
  • Nougat
  • Nut butters, nut oil, paste
  • Pecan
  • Pine nuts (pignolia, Pinion)
  • Pistachio
  • Walnut

These "Nuts" are not included in Tree Nuts:

  • Coconut
  • Water chestnut
  • Nutmeg
  • Mace

Prevalence of Tree Nut Allergy

At least 0.6% of the general population is found to be allergic to at least one tree nut.

Age of onset
Most children develop their allergic reactions to tree nuts some time between 2-4 years of age.

Cross-reactions
In one study of peanut-allergic children, 19 of 32 challenge-positive children were skin tested to tree nuts; 12 of 19 had a positive skin test to one or more nuts:

  • Walnut 11
  • Filbert 10
  • Cashew 9
  • Almond 6
  • Pecan 6
  • Pistachio 6

None of these children experienced a reaction on double-blind challenge to a nut.

Most physicians dealing with peanut allergy also ask that the patient avoid tree nuts as well. The reason is that there a significant number of children who initially had only peanut allergy and did not avoid tree nuts, and then went on to have an allergic reaction to tree nut.

Cross-reactions between tree nuts

For convenience it is better for someone who is allergic to any tree nut to avoid all of them in his or her diet. It is very difficult to determine which one of the tree nuts is contained in any particular food. Because some food manufacturers frequently use multiple tree nuts in their factories, the likelihood of contamination with another tree nut is higher.

Results from lab studies indicate that the protein in all tree nuts that cause allergic reactions is very similar. The proteins that primarily cause allergic reaction are seed storage proteins that are concentrated in the nut of the tree. They mainly exist to provide energy to the next life cycle of the plant. This important medical finding indicates that the possibility of developing a reaction to more than one nut is greater.

From a medical standpoint, there is no reason to avoid coconut, nutmeg, or water chestnuts if you are allergic to any of the tree nuts. There is no evidence to suggest that acorns should be avoided either (some recommend avoiding it).

Diagnosis of Tree Nut allergy

Skin Prick Test or CAP RAST is very reliable.

Sesame Allergy

Sesame (Sesamum Indicum) is becoming increasingly popular in Western diet. Those small seeds that characterize hamburger rolls & other bread products are sesame. The sweet nutty flavour of sesame seed increases when it is mildly toasted.

Sesame is also known as Benne, Gingelly, Til or Teel, Simsin and Anjonjoli on foreign products.

Sesame seeds are extremely potent allergens and can cause severe allergic reactions (anaphylaxis) in susceptible individuals. Sesame is used extensively in the food industry and the seeds present a danger because of their versatility. They have been identified in non-sesame products, especially bread, due to cross-contamination.

Humous, Tahini, and Halvah are three very popular sesame products which are sometimes added to other foods without any clear declaration. Other common sources of sesame include:

  • Bakery products
  • Biscuits
  • Confection bars
  • Muesli
  • Dips
  • Sauces
  • Sausages
  • Processed Meats
  • Vegeburgers
  • Chutneys
  • Stir Fries
  • Rissotos

Cross contamination from sesame seed products made on the same line as non-sesame products is becoming more common.

The popular herbal drink, Aqua Libra, contains sesame.

Sesame oil is used unrefined in food products and as a result it is hazardous to those allergic to sesame. The prize oil possesses unique properties. It resists rancidity and is extremely popular with Chinese chefs.

Sesame oil is used in pharmaceutical products, such as plasters, liniments, ointments and soaps. It is used in cosmetics, where it may be listed as sesamum indicum.

Eating out requires great caution as sesame is so widely used these days.

Under the current food labelling regulation, known as the 25% rule, small amounts of sesame may be present in any foods without any clear declaration.

The generic 'vegetable oil' complies with the current regulation.

Awareness of sesame allergy is low. It is less common than peanuts, but allergic reactions can be just as severe.

Management

Use the same precautions for Peanut Anaphylaxis.

Credits for the Sesame Allergy section in this article

'Reproduced with permission from work done by Maggie Spirito Perkins, British Allergy Foundation'.

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