Lipid transfer protein (LTP) allergy / syndrome patient information leaflet

What is LTP?

Lipid transfer proteins (LTP) are a group of very similar proteins found in various plant foods such as fruits, vegetables, nuts, seeds and cereals. They protect plants against insects and organisms like viruses and bacteria that cause diseases. They are resistant to being broken down by normal digestion, acid and heat etc.

What is LTP allergy / syndrome?

LTP allergy / syndrome is a complex food allergy caused by reactions to plant foods. It is not well-known. It was historically thought to be confined to Southern Europe or Mediterranean Europe, particularly Spain, Greece and Italy. But, it is increasingly recognised as a cause of food allergy beyond Europe. Reactions can occur to a single plant food or more.

It usually occurs in older children and adults.

What foods can cause symptoms?

Although any plant food can potentially cause allergic reactions, the common culprits include apples, grapes, peanuts, walnuts, hazelnuts, almonds, dried fruit peel, tomatoes and fermented / concentrated / preserved / processed plant foods. Most LTP content is found in the peel and pips of plant foods.

LTPs are not broken down by digestive enzymes or through cooking or processing.

Therefore, people with LTP allergy, cannot eat the culprit foods in any form (cooked, roasted, processed, juiced, canned, dried, fermented or crystalized).

What are the symptoms of an allergic reaction?

Symptoms can range from mild to severe. They usually begin within 15 to 30 minutes of eating. In some cases, for people sensitised to LTP, if an external factor known as a “co-factor” is present, symptoms may be delayed until 2 to 4 hours after eating.

Symptoms include:

• Swelling of lips, eye lids, tongue, mouth and throat
• Hives / urticaria (nettle rash)
• Stomach pain, nausea, vomiting
• Occasionally, severe (anaphylaxis) – choking sensation, difficulty breathing, swallowing and talking; feeling faint / dizzy and in extreme cases collapse.

What other factors (co-factors) can contribute to an allergic reaction?

LTP allergic reactions are more likely when another factor known as a “co-factor” is present. They enhance reactions. “Co factors” include alcohol, exercise, stress and non-steroidal anti-inflammatory drugs / pain killers (NSAIDs) like ibuprofen and naproxen.

What foods do I need to avoid?

It is difficult to predict which foods may cause reactions as not all LTP-containing plant foods trigger symptoms, and the amount of LTP in foods vary from food to food.

Reactions tend to vary from person to person and only one or two plant foods may cause reactions. You therefore only need to avoid plant foods which have caused reactions.

We cannot use skin tests or blood tests to screen or predict what plant food foods may trigger allergic reactions.

People at high risk of a severe reaction are usually given an emergency treatment plan on what medication to take and when. They are usually prescribed an adrenaline auto-injector (AAI), to carry with them along with anti-histamines. Those with asthma should also carry their inhalers.

How can I keep safe with LTP allergy?

• Avoid particular LTP plant foods that trigger a reaction, in all forms (raw, cooked, processed or fermented).
• Avoid use of non-steroidal anti-inflammatory pain killers like ibuprofen, 2 hours before and after eating.
• Avoid exercise 4 hours after eating plant foods.
• Avoid alcohol when eating and after eating plant foods
• If you have avoided specific plant foods for a long time, re-introduce them in your diet in small amounts over time.
• If you are at risk of severe reactions or anaphylaxis, carry your prescribed emergency medicines (anti-histamines, adrenaline auto-injector and inhalers if asthmatic) at all times.
• Once adrenaline has been administered, an ambulance must be called for further treatment in hospital, if necessary.

For further support

• Allergy UK website (opens in a new tab)
• Allergy UK Helpline (opens in a new tab): Monday to Friday, 9am to 5pm 01322 619 898 / Allergy - UK - Info (opens in a new tab)