Archive for the ‘Nut Allergy Science’ Category

Allergic Reactions: What Happens?

For information about nut allergies from someone who knows what they are talking about, I spoke to Claire Dunne, a fourth-year medic in training at Cardiff University. I’ve read many online articles about nut allergies which are hard to understand and very confusing for someone like me who does not engage with anything remotely Science-like! So I wanted a simple explanation of nut allergies, and how they work.


Nut Bowl: [Image Courtesy of IainBuchanan]

Anaphylaxis, Intolerance and Reaction Rates

I first asked about the rather confusing and terrifying concept of anaphylaxis. Claire said:

“It’s like a whole body version of a rash, which results in your blood pressure dropping steeply and could even cause the airway to close. The blood vessels become leaky, releases fluid into tissues and everything swells. That is the visible swelling you can see when someone is having an anaphylactic reaction. You are more likely to get an anaphylactic reaction than with most other allergies.”

I wanted to know why some people are ‘intolerant’ of nuts in the first place. How do nut allergies occur?

“Sufferers are not allergic to the nut itself, but a specific protein within nuts. When you are first exposed to nuts, you don’t have a visible reaction but your body produces white blood cells (mast cells) with ‘weaponry’ specific to the protein in the nut you ate, because it identifies it as a threat, which it shouldn’t. These cells then lie in wait in the body and if you are exposed again they are ready to attack immediately by releasing the chemical histamine, which is what causes the symptoms of an allergic reaction.”

Something that has always intrigued me is why some people have a reaction when they smell or come into contact with the nut, when others only react when they consume it. Claire said that there is no formulaic answer:

“It is completely dependent on the person. With more serious allergies people are allergic to particles of nuts that are in the air, and they have a reaction to it. It depends where mast cells are activated, in one place or everywhere in the body. The only way you can tell how allergic a person is, is to do a challenge test [be exposed to it, in other words]. This is not often done with nuts because of the high risk of anaphylaxis, but with other allergies like lactose, for example, it is more common.”

With these, an allergic reaction will constitute a small illness for the person not a life-threatening reaction, so it is safer to do it, Claire tells me.

Eating Nuts with No Reaction?

I wanted Claire to explain how it is possible for nut allergy sufferers to consume nuts and not have a reaction. In my own case I had a Grade 2 RAST Test reading for hazelnuts but was fine after eating Nutella. According to Claire, there could be a number of reasons why this happened.

“The first is that people who have allergies to a specific nut might not be adequately exposed to it to trigger a reaction. This can happen even if they consume it. The food itself may have very low nut content so a person might not have a reaction. Or, the mass of food eaten is very small, so if it is consumed in such a small amount, put simply, it might not be enough to trigger an allergic reaction.”

The second reason I found particularly interesting, and concerns the cooking process of food. Claire said: 

“When food is cooked, it can affect the proteins in it. They become denatured or altered into something that a sufferer is not allergic to.”

Cake Closeup

Baking and Cooking MIGHT Denature Proteins in Nuts: [Image Courtesy of su-lin]

This makes sense thinking back to Claire’s explanation of why people are allergic to nuts. Sufferers are not allergic to the nut itself, but instead proteins inside it. So if these proteins are changed in the cooking process, you could effectively eat a nut without being allergic to it. “But this does not mean it is safe to eat nuts if they are cooked. This is just a theory some people believe” Claire stressed.

Growing out of Allergies

There is a lot of online content about growing out of allergies, but I don’t know how much of it I can believe. Claire tried to clarify the matter for me:

“It is possible to grow out of allergies. It is quite common for asthma and hay fever sufferers, for example, to find that their situation improves. But nut allergies are funny [odd, certainly not laughable!]. It is possible to grow out of them, but you usually don’t – again because it is usually an anaphylactic reaction. Most people have a first exposure to nuts when they are young and they avoid nuts in their diet from then onwards. So even if you have grown out of a nut allergy it is hard to tell that you have, simply because you go out of your way to avoid them.”

I then asked Claire about something which I have heard of, where a sufferer can, in theory at least, make their body build a tolerance to nuts.

“It’s called Desensitisation Immunotherapy. It has to be done in hospital, in a controlled environment. Your body is injected with tiny amounts of the substance you are allergic to and it gets used to it over time. It will come to a stage where the body doesn’t see it as a threat any longer and an allergic reaction is not triggered when it is exposed to the substance. Again though, it is more common in asthma and hay fever and dangerous for nut allergy sufferers. It is a long process where you have to have many sessions of the Immunotherapy in hospital.”

It will be a long time in the future where such treatment becomes commonplace for nut allergy sufferers, I am assured.

And Finally…

… a very quick word on the importance of EpiPens, which I intend to write an entire post about in the future.

“They contain adrenaline, basically. They can give someone having an allergic reaction that extra bit of time while the Emergency Services are getting to you.”

They are vital, in other words.

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