You are here

Q. Within the last month I've had four allergic reactions that are limited to my lips, skin around the lips, and chin. The area becomes inflamed, chapped, cracked, painful, and itchy. No other area is affected. I couldn't figure out what was causing it because I was eating different foods each time it happened. I started doing some research, and I was looking up common fruit allergies, since I eat a lot of fruit. Lately (in the past 5 months) I've been eating a lot of mangoes. I came across an article about mango allergy and the symptoms fit pretty well with what I’ve experienced. However, my allergic reaction does not happen immediately when I eat the mangoes. This last time, I had eaten a mango the day before. The same is true for the other occasions; I had a mango either a day or two before the reaction happened. Is it possible that the mango is causing my reaction a day later? I have a rash right now, and it has lasted three days. It's easy enough to quit mangoes, but I'd really like to know the cause.

A. Based on the description you provided, it sounds like you may be one of the unlucky people who are allergic to a chemical compound called urushiol.  This chemical is actually an allergen that is found in poison ivy, poison oak, and poison sumac as well as several other plants including mango (mainly in the skin) and cashew nutshells.  In around half of people exposed to it, urushiol causes allergic contact dermatitis, or an allergic rash.   Allergic contact dermatitis can be a delayed reaction up to 48 hours after exposure to the allergen, although more frequent exposure tends to make the reaction occur more quickly.

Given the timeline and description of your symptoms, I agree that you may be experiencing allergic contact dermatitis to mangoes.   Your allergist can aid in your evaluation and in managing your symptoms.

Be aware that you may also be a have strong reactions to poison ivy and similar plants – remember the phrase, “Leaves of three, leave it be!” when you are outdoors to help you identify and avoid these plants. 

Q. I’m Canadian, and while on holiday in Ecuador, I ate fish in a restaurant for lunch. I don’t know what kind of fish it was, but within minutes of eating it, I felt very nauseous. I stopped eating, but continued to feel worse. I got very dizzy and could not stand up, and I broke out into extreme perspiration all over my body, even though it was a cool day. When I was able, I returned to my hotel and slept for several hours. I love eating fish (though I avoid shell fish) and have never had anything like this happen. Could this have been an allergic reaction? Was it related to eating a kind of fish I’m not accustomed to?

A. Based on the description you provided, it sounds as though your symptoms may have been a toxic reaction to the fish you consumed, rather than a true allergic reaction.  One food borne illness related to fish is called scromboid poisoning, or histamine toxicity. Scromboid poisoning is related to the decay of histidine, an amino acid that exists naturally in fish, converting over time at warm temperatures to histamine. Histamine is the natural chemical responsible for allergic reactions. 

Scromboid poisoning typically begins within 5 to 30 minutes after eating spoiled fish, although sometimes it can be delayed for as long as two hours. It can resemble an allergic reaction, often starting with GI symptoms, such as nausea; followed by neurologic symptoms, such as dizziness. Symptoms are generally self-limited, but may last for several hours.

You also mentioned that you avoid shellfish. Is this due to a previous history of a shellfish reaction? If so, your allergist can perform testing to confirm or refute a shellfish allergy and help you manage and avoid future reactions.  Your allergist can also evaluate your recent adverse symptoms to the fish you consumed in Ecuador further.  

Q. Is it possible for a shellfish allergy to go away? I developed an allergy to shrimp and lobster in my 20s. Now I'm 65, and I'm wondering if there is a chance the allergy will ever go away.


Q. Can eating too much peanut butter give you an allergy?

A. No, thankfully there is no relationship between consuming large quantities of a food and the development of a food allergy. If there were, a lot more people would be allergic to pizza! Eating a food is actually one way that we maintain the body’s tolerance to the food. The mechanism for how we develop allergies to foods that we have tolerated in the past is still not clear. Allergy to food can develop at any time in a person’s life, but it most commonly occurs in childhood and less commonly as an adult.

Q. My 12-year-old son suffers from sinusitis and allergies to pollen, grass and fabric softener. He had boiled eggs for lunch today and 15 minutes later had hives over his entire body, including his genitals and the bottoms of his feet, and his lips and eyes swelled up. The hives only seem to last a few hours, but they itch and seem to spread. I took him to the clinic immediately after school, where he was prescribed Allergex and Paracetamol. He has been eating eggs all his life and has never had any reaction to them before. What can we do to ease the itching of his hives? Should he avoid eggs in the future?

A. It's good that you took your son to be evaluated immediately and that he is improving.

Your son’s hives and swelling are also called urticaria and angioedema.  Hives are itchy pink or pale swellings that appear as welts, and can occur on any part of the skin.  Each individual hive typically lasts minutes to hours before fading away without leaving a mark.  New hives can arise as old ones fade away.  They can vary in size from a few millimeters to inches, and can blend together to form larger swellings. 

Hives result from blood plasma leaking through small gaps between the cells lining small blood vessels in the skin.  Histamine is a natural chemical released from allergy cells, which lie along the blood vessels in the skin.  Histamine causes the itching, swelling, and red color of hives.  The angioedema, or swelling of the deeper layer of skin, occurs through a similar mechanism.  With generalized urticaria and angioedema, topical treatments do not tend to improve symptoms; oral antihistamines are frequently needed.

Food allergy is one of the most common causes of acute hives.  Egg are a very common food allergen for children.

Your son should be evaluated by his allergist for his recent symptoms.  In his case, the cause of his reaction may have been the egg ingestion, or another ingestion that he may not have recalled immediately.  Insect stings and medications are other common triggers for acute urticaria and angioedema. 

Your allergist will likely perform testing, which could include skin prick testing and/or blood testing to various suspected allergens.  Once the allergen is identified, your allergist will help you decide what avoidance measures to take.

Because you suspect egg, avoidance of egg until your son sees his allergist would be a safe and conservative strategy.

Q. I have been allergic to “nuts” my whole life, but as I have grown older, have realized various distinguishable reactions to different nuts if I consume them. I have also noticed that I am allergic to some nuts, but not all – and I am really interested in discovering any relationship that may be present between each nut I am allergic to. When I eat cashews and pine nuts, I experience an “itchy” feeling inside my mouth, which also goes into my chest. I also feel like I need to throw up, but can't. When I eat macadamia nuts, however, I experience extreme swelling inside my mouth, verging on anaphylaxis. I have never consumed large amounts of any of the above-mentioned nuts, but I am sure that if I did, I would have an anaphylactic reaction. The reaction following consumption of the above nuts is nearly immediate, so I am usually able to detect the sensation fairly quickly and refrain from consuming any more. From my brief research, I have discovered that cashews and pine nuts are not actually considered nuts. I would like to know if you are aware of any similarities between each of the 3 nuts above, so I am able to pinpoint what it actually is that I am allergic to.

A. Being allergic to tree nuts is becoming more common.  When a person is allergic to one tree nut they may not necessarily be allergic to all other tree nuts.  Patients with cashew allergy may develop adverse reactions to other items such as pistachios, mangoes, and poison ivy.  Pine nuts have been reported to cross react with mugwort, wormwood, and sagebrush.  Interestingly, macadamia nuts have allergenic proteins that cross react with hazelnuts (filberts).

Q. Will a nursing baby whose mom eats eggs have an allergic reaction to the eggs?

A. It has been clearly demonstrated that intact food allergens can be passed through breast milk and cause allergic reactions, particularly eczema in food allergic infants. Mothers should avoid ingesting those foods that trigger allergic reactions in their infants during or after breastfeeding.

Q. A few days ago I ate one piece of watermelon and my whole throat started feeling itchy and puffy. The same thing happens with cucumber, kiwi fruit, avocado, and bananas. What might be the cause of this?

A. Based on the history you provided, it sounds like you may have a condition called “oral allergy syndrome,” sometimes also called pollen-food sensitivity syndrome.  Oral allergy syndrome is caused by an allergy to cross-reacting proteins found in pollens and in the foods you described. Many of these proteins are heat, acid, and enzyme labile; meaning that when you eat the food, they can cause your mouth to itch but the acid and enzymes in your digestive system break them down before your body can absorb them.  For this reason, oral allergy syndrome is rarely associated with symptoms beyond the oral cavity such as hives, breathing difficulty, or anaphylaxis. In many cases, heating the foods will denature the proteins. For example, a cake baked with banana may not cause symptoms in some patients who have symptoms with fresh bananas.

The treatment for the oral allergy syndrome is to avoid the foods that make your mouth itch. Some foods, such as apples and melons, store their proteins in the peel or rind, so removing the outside part can help. Finding alternative fruits and vegetables that do not cause symptoms is recommended.  Your allergist will help to guide your evaluation and provide you with personalized recommendations.  

Q. I can eat soy products (i.e., soy sauce), but when I try to drink soy milk, I experience an itch in my mouth (usually after a couple minutes). Should I stop drinking soy milk?

A. Based on the history you provided, it sounds like you can tolerate some soy products, but not soy milk. The answer to whether you should permanently stop drinking soy milk depends on a number of variables, including the amount of soy milk needed to cause the reaction, the consistency of your symptoms with soy milk, whether other foods are involved, and whether you have other accompanying symptoms beyond oral itching.  

If you only have oral itching with no other associated symptoms, then you may have what is called “oral allergy syndrome.”  Oral allergy syndrome manifests as isolated oral itching due to a food protein (such as soy) that cross reacts with the protein in a pollen (such as birch pollen).

The best way to find out if your symptoms are being caused by oral allergy syndrome is see an allergist, who will go over your history in detail and consider allergy testing to pollens and/or soy.

As soy is a common food in many diets, knowing which foods to avoid would help you manage your symptoms.  In the meantime, conservative avoidance of soy, until you have an appointment with your allergist, is the safest course of action. 

Q. Is it possible to develop a tree nut allergy at 43? If so, why, and is there hope of reversing it?


Tree nut allergies are common in both children and adults. Approximately 9% of children with a tree nut allergy eventually outgrow their tree nut allergy.  In an adult, “outgrowing” or “reversing” a tree nut allergy is not common. 

Tree nuts can cause severe, potentially fatal, allergic reactions.  To prevent an allergic reaction, strict avoidance of tree nuts is essential.   A person with an allergy to one type of tree nut has a greater chance of also being allergic to other tree nuts.  Therefore, many experts advise patients with an allergy to a tree nut to avoid all tree nuts.  Your allergist can help you with personalized recommendations for your care. The Food Allergy Research & Education (FARE) website is also an excellent resource.

Q. Is it safe for a science class to plant peanuts when a child in that class is allergic to peanuts? Even if the child is separated during the planting portion, wouldn't the risk of them contaminating the class be too hazardous?

A. As long as the child doesn’t eat the peanut and washes her/his hands after contact with the peanut shell, the risk of an allergic reaction would be extremely low.

However, this situation may impose a risk if the child has reacted previously from exposure to raw peanut in the shell by inhalation or touch. In addition, having peanuts in the classroom may raise concerns among parents, and the project may be perceived as being insensitive to the child. As such, we do not recommend planting peanut shells as part of a school project.

Q. I'm planning to make fried chicken using peanut oil. I recently read that peanut oil doesn't cause peanut allergy reactions. Is that true? Is there something on the label of the oil or the packaging that will let me know that?

A. Most individuals with peanut allergy can safely eat highly refined peanut oil. This is not the case, however, for cold-pressed, expelled, extruded peanut oils. If you are allergic to peanuts, ask your allergist whether you should avoid peanut oil. For more information, the Food Allergy Research & Education (FARE) website is also an excellent resource.


Q. I am allergic to the protein in milk, but when I went to see an allergist, all he told me was to stop drinking milk or any dairy products. Is there anything else I can do? Medicine? Something else?

A. Unfortunately, avoidance of the food allergen is the only way to protect against an allergic reaction to a food at this time.

However, there is good news. Clinical trials of promising new treatments are underway. Trials including sublingual immunotherapy, oral immunotherapy, and herbal formulas are being conducted at major medical centers nationwide. There may be additional therapies for management of food allergies in the future.