The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 53

66. How long does it take to react to a trigger?

There isn’t a straight answer to this. The time it takes to react to a trigger is hugely variable. It depends upon the trigger; the strength of the reaction it triggers; the patient; the medications they take; their lifestyle; and other activities that may increase or decrease reactivity. As we have discussed before, the reaction you see from a trigger is often the cumulative result of how much histamine you have circulating at the time, which can be affected by many other things. Reactions can happen immediately or several days later. It is not unusual for mast cell patients to react days later, especially to things they have ingested. This logically makes sense to me as a result of the trigger still being in the GI tract but there is still not definitive proof that explains why you can react days later.

67. What physical things trigger mast cells?

A lot of physical things trigger mast cells. The exact reasoning for why some of these things trigger mast cells is still not well understood. However, these triggers are documented in literature, often as triggers for physical urticaria (hives caused by physical triggers) and/or angioedema (swelling). While reactions to these triggers often start in the skin, the mast cell activation can spread to other mast cells elsewhere in the body. Additionally, patients may not have skin symptoms but have reactions to the following triggers.

Heat and cold can both activate mast cells. Hot water and cold water are both common triggers. Water in general is a trigger for some. Emotional stress is activating, as is various forms of physical stress, including exercise, surgery, physical trauma, infection, or increased activity of another disease. Sweat can be a trigger, regardless of whether the patient is sweating from exercise, heat, or something else. Pressure on the body, even mild pressure, can cause mast cells to release chemicals. Sunlight and vibrations are also known triggers. Mast cell patients are recommended to premedicate before any medical procedure, including imaging like ultrasounds, X-rays or MRIs, as patients have reported activation from these things. Changes in barometric pressure, such as from a change in weather or a storm, are often reported by patients to cause symptoms.

For more detailed reading, please visit the following posts:
Chronic urticaria and angioedema: Part 2

The Sex Series – Part One: Kissing and allergic reactions

The avenues by which a person can suffer symptoms as a result of sex are almost endless.  I am asked often about the mechanism by which mast cell patients can react to foreplay or intercourse. The reason it has taken so long to put this series together is not because of a dearth of information, but because there is so much.  The research on this topic is deep, if not always to the point: Why do some people react badly to having sex?

There are a number of reasons why sex can cause allergic symptoms, which explains why intimacy is often fraught with anxiety for mast cell patients.  So let’s start with the entry level: kissing.

It is widely accepted that kissing can transfer allergens via saliva, or contact between skin or oral mucosa.  Allergic reaction after kissing is not even especially unusual.  5-12% of IgE food allergic patients have had at least one reaction after kissing.  Peanuts, walnuts, and tree nuts are the most common offenders.  Rash around the mouth, hives around the mouth, flushing, angioedema of lips, mouth, tongue and throat, wheezing and hives all over the body have all been reported in this situation.  Usually symptoms present within minutes, but there are literature references to reactions developing up to three hours later.

In a group of 26 volunteers that ate peanut butter, the protein reached its highest concentration in saliva five minutes after consumption.  After an hour, the protein was undetectable.  Several methods for clearing the protein were tested.  Brushing teeth, rinsing mouth, or both, waiting an hour after consumption, and waiting an hour and then chewing gum, all reduced protein concentration by over 80%.  However, waiting one hour after eating was still the most effective way to clear the protein from the mouth.

Though much less common than transfer of food allergens, it is possible to transmit medications via saliva. In literature, all reports of this phenomenon involve ingestion of β-lactam antibiotics, including penicillin derivatives.  In these cases, the patients had symptoms of oral allergy syndrome with hives over large parts of the body.

The quality of the kissing is certainly a factor.  How deep is it?  How much hard? How much friction?  How wet?  Mast cell patients often react to physical stimuli like this.  It’s not hard to imagine a situation where the pressure and heat of kissing cause local mast cell degranulation.   I found a (non-scientific) article describing a woman with aquagenic urticaria who reacts to kissing because it’s wet.  For patients allergic to sweat, that could also cause a kissing reaction.

I feel like I should throw out there that you can react to allergens returned to the mouth by vomit.  Mostly because there isn’t really anywhere else to put it.  So it’s here.  The warning about vomit is in the kissing post.  How did this get to be my life?

BUT GUESS WHAT GUYS?!?!?!? Kissing can also be good for allergy patients.  One study reported that that kissing decreased wheal response (the formation of red swollen areas) was decreased 28-34% in patient allergic to dust mite and Japanese cedar pollen.  This patient group had allergic rhinitis and atopic dermatitis.  It didn’t decrease the response to injection of histamine, which means the benefit from kissing in this study is not directly blocking histamine.  Plasma levels of neurotrophins were decreased in these patients.  Neurotrophins have a complex relationship to mast cells, so it’s possible that neurotrophins block something that tells mast cells to release histamine.

I know everyone wants to know – how can I kiss safely? So hang in there, because it’s coming.  Along with the answers to all of the “embarrassing” sex questions I have ever been asked.


Liccardi G, et al. Intimate behavior and allergy: a narrative review. Annals of Allergy, Asthma & Immunology 2007; 99: 394-400.

Maloney JM, et al. Peanut allergen exposure through saliva: assessment and interventions to reduce exposure. J Allergy Clin Immunol 2006; 118: 719-724.

Liccardi G, et al. Drug allergy transmitted by passionate kissing. Lancet 2002; 359: 1700.

Sonnex C. Genital allergy. Sex Transm Infect 2004; 80: 4-7.






Chronic urticaria and angioedema: Part 2

CU lesions are swollen pink or red wheals, of variable size, often with surrounding redness. They are generally itchy rather than painful or burning. Angioedema is not itchy, brawny, of a non-pitting quality with indistinct margins and without redness.

There are a number of chronic urticaria and angioedema (CU) subsets that are triggered by environmental sources. These are called physical urticarias.

In aquagenic urticaria, patients develop hives after contact between water and the skin. Temperature is not a factor in this type of urticaria. The hives are generally “pinpoint”, measuring 1-3mm. This is confirmed by applying a water compress at near body temperature to the skin of the upper body for 30 minutes.

Cholinergic urticaria also causes pinpoint hives, but these hives are surrounded by large flare reactions as a result of increased body temperature. Exercise, sweating, emotional stress, hot baths and showers are all frequent triggers of this subtype. Cholinergic urticaria can be benign or life threatening. Testing involves exercise or hot water immersion as these activities raise the core body temperature.

Cold urticaria results in hiving when the skin is exposed to a cold source. Patients may have systemic reactions in the event of full body exposure to the cold (swimming in cold water, etc). This is tested by placing an ice cube on the patient’s skin and waiting for a reaction, which occurs when the skin starts to warm.

Delayed pressure urticaria/angioedema presents as swelling, which may be painful, after the skin is exposed to pressure. While 4-6 hours is a more typical duration for symptoms to present, in some patients it can take 12-24 hours. Working with tools, sitting on a bench, wearing tight clothing, and carrying a heavy purse are all representative triggers. Testing for this subtype involves placing a 15 lb weight on the patient’s shoulder for 10-15 minutes, then waiting for response. Angioedema at the site that evolves following this test is considered a positive test, regardless of whether or not weals are present. This type can be difficult to treat.

Dermatographia is the most common type of physical urticaria. 2-5% of the general population have dermatographia.   Stroking the skin firmly causes a weal and flare reaction where the skin was touched. It does not usually require treatment.

Exercise induced anaphylaxis has two types: those in whom anaphylaxis in provoked strictly by exercise, and those in whom anaphylaxis is triggered when a specific food is consumed prior to exercise. Cholinergic urticaria can also be triggered by exercise, so it is important to distinguish between the two. Exercise anaphylaxis can only be triggered by exercise, whereas cholinergic urticaria results if the patient becomes too hot. People with exercise induced anaphylaxis need to carry epipens and must not exercise alone as reactions can be severe.

Solar urticaria is the development of hives when the skin is exposed to sunlight, generally within minutes. Solar urticarial is further divided in subtypes based upon which wavelengths of light are triggering to the patient. Testing involves lightbox exposure to isolated wavelengths of light. It is distinct from polymorphous light eruption, in which onset is often delayed and can last for days. It can cause papules, papulovesicles and plaque manifestations on the skin.

Recall urticaria is hiving at the site of a previous sting or injection when exposed again to the same trigger.

Vibratory angioedema causes itching and swelling when the skin is exposed to a vibration source. This specific type can show a familial trait. It is confirmed by showing a response after use of a vortex mixer (a piece of lab equipment that mixes solutions in tubes).



Jonathan A. Bernstein, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol Volume 133, Number 5.

Usmani N,Wilkinson SM. Allergic skin disease: investigation of both immediate and delayed-type hypersensitivity is essential. Clin Exp Allergy 2007;37:1541-6.

Zuberbier T, Maurer M. Urticaria: current opinions about etiology, diagnosis and therapy. Acta Derm Venereol 2007;87:196-205.