As well as being Leap Year Day, the 29th February this year also marks the 11th annual Rare Disease Day.
The international event run by the European Organisation for Rare Diseases (EURORDIS) aims to increase awareness among both the general public and key decision makers of some of the world's rarer medical conditions.
Here on the blog we like to do our bit. And with allergy season (otherwise known as spring) just around the corner, we decided to delve a little deeper into this subject and take a closer look at some of the rarer forms of allergy.
To do this, we got in touch with Holly Shaw, Nurse Advisor at Allergy UK, to get her expert opinion; not just on the rarer forms allergies take, but also on allergies as a whole, including how to get a diagnosis, and how to effectively manage them.
Allergies are becoming more common with around 30 percent of the world’s population experiencing some form of allergy during their lifetime.
Of that 30 percent, the majority of people are diagnosed with a common allergy such as hay fever or animal dander.
However, there are those who live with rarer and lesser known allergies where little is understood about what causes them and how to treat them.
So is there any one single thing that all allergens have in common?
‘The majority of allergens are protein based.’ Holly explains. ‘It is the protein in foods and other substances that causes the body to recognise that substance as harmful and mounts an immune response in the form of an allergic reaction. So, it is possible to have an allergic reaction to any substance.’
Why do rare allergies occur?
Research into the causes of allergies is ongoing but Holly highlights that genetics and our environment may both play a part:
‘There is a growing body of evidence to suggest that our genetic and familial tendency to develop an allergy (atopy) and the environment and lifestyle we lead have roles to play in developing an allergy.’
As you might expect however, the nature of rare allergies makes it tough to carry out detailed research:
‘Due to smaller patient populations enduring rarer disease forms it can be difficult to capture data and carry out research in this area.’
Link with asthma
What we do know is that asthma is one condition commonly linked to allergies, which may also be a factor for those with rarer forms.
‘People who have asthma can also have other types of allergies including rare forms. A genetic predisposition to developing allergic conditions including food allergy, asthma, eczema and hay fever is called atopy. Being allergic can run in families, however it does not mean that this will happen; it just increases the likelihood of a family member developing an allergy.’
‘Where asthma and a food allergy coexist it is important that both are well managed due to the increased risk of a more severe reaction occurring in a person who already has a sensitive airway. Having strategies in place to avoid triggers and manage an allergic reaction in patients where food allergy and asthma co-exist is vital.’
So what are some of the rarer triggers for allergic reactions, and what coping strategies are available to those who are susceptible?
1. Semen (seminal plasma hypersensitivity)
This rare reaction is caused by proteins in male sperm.
Although thought of as a rare allergy, one small study carried out several years ago suggested that this condition could affect up to 12 percent of women.
Symptoms tend to occur following sexual intercourse where sperm comes into contact with the vagina.
Those with the condition report redness, swelling, itching and pain.
This allergy causes similar symptoms to those found in some sexually transmitted infections, vaginitis and fungal conditions. This means that it can be frequently misdiagnosed.
One obvious factor which can indicate whether a sperm allergy is present is condom use. If sex without a condom takes place and symptoms flare up, then that could be a sign.
This allergy can lead to relationship strain, particularly when a couple is trying to conceive. The allergy is not thought to have any effect on female fertility, but artificial insemination might be considered an option for women with severe cases.
Those who think they may have an allergy to sperm should speak to their doctor, who may refer them to an allergy specialist or gynaecologist.
2. Water (aquagenic urticaria)
With only a handful of known cases worldwide, the water allergy is among the rarest of the rare.
Holly tells us:
‘Aquagenic urticaria is a rare form of physical urticaria, where contact with water can cause hives, a rash and/or angioedema. The hives or rash is often described as very itchy, uncomfortable and can be painful.’
Frightening as it sounds, it doesn’t need to be any one particular type of water; all types can be responsible.
‘Aquagenic urticaria can be triggered by exposure to water from bathing, showering, swimming, exposure to rain, or in more unusual cases, on exposure to sweat or tears. The water source responsible for inducing the urticaria can be fresh, salt or chlorinated water.’
Water is obviously an essential part of daily life which can make living with a water allergy considerably challenging. Bathing, washing up and even stepping outside during a rain shower can all cause a painful reaction.
Not much is known about this allergy but some think that it could be triggered by altered histamine levels. However, antihistamine medications tend to offer no respite, which seemingly contradicts this theory.
Due to the rarity of the condition, obtaining a correct diagnosis can be difficult, as Holly explains:
‘Aquagenic urticaria may co-exist with other forms of urticaria making diagnosis a challenge.’
Those who aren’t able to determine the cause of their urticaria with the help of their GP may be able to do so via an allergy specialist (details provided at the bottom of this article), who may also be able to provide treatment advice.
3. Sunlight (polymorphic light eruption, or PLE)
This particular allergy presents as a rash which can take on various forms (large or small spots, or patches) following exposure to sunlight. This can then lead to blisters.
The rash tends to appear one or two days following sun exposure and usually surfaces in spring-summer months.
Up to 10 percent of people may experience some level of PLE which makes it quite common. However, a much smaller number of people living with PLE experience more severe year-round reactions.
Those suspicious of PLE should see their doctor who may refer them to a dermatologist. Phototesting using differing wavelengths of UVA and UVB light is sometimes carried out in an attempt to rule out other potential conditions.
There is no cure for PLE and symptoms can make those affected feel self-conscious. It can also limit the activities a person can take part in, especially during sunnier months.
More extreme cases of PLE can have a serious effect on quality of life if it hinders their ability to go outside. In such cases, expert advice from an allergy specialist should be sought.
4. Sweat (cholinergic urticaria, or CU)
Sweat induced urticaria produces a wheal and flare reaction on the surface of the skin.
This tends to occur when the body’s overall temperature is increased, such as during exercise or stressful situations, taking a hot shower or upon entering a hot environment (such as a sauna or a kitchen).
Mild cases of CU can be fairly common but a severe reaction is more unusual.
The cause is thought to be linked to an immune system antibody overreacting to raised skin temperatures.
The best way to prevent a CU reaction is through avoidance which can lead to some lifestyle restrictions. These changes can be difficult to adjust to for some patients who may require specialist support.
5. Deodorant (axillary dermatitis)
Cosmetic product allergies are fairly commonplace with up to 23 percent of UK women reporting some sort of dermatitic reaction. That being said a specific allergic reaction to deodorants or antiperspirants used on the underarm area is rarer.
The majority of people with this condition will likely have other cosmetic based allergies to fragrance or essential oils.
This is another allergy which can make those with the condition feel self-conscious, due to its restrictive effects on the use of deodorising products.
The condition can be difficult to manage and finding a suitable alternative product may take time; advice from dermatological specialists is recommended.
6. Fish odour
It is estimated that one in 200 people have an allergic reaction when they ingest seafood, making it a relatively common allergy.
However, of this number around 15 per cent may experience a reaction to the odour produced by fish and seafood alone.
This type of response to a smell is unusual and only tends to happen when seafood is being cooked, resulting from the vapours and steam being produced.
Fish and seafood release very small proteins called amines during cooking, which can cause allergic reactions in the airways and lungs.
Avoidance is key wherever possible; but being allergic to a smell can make it particularly difficult to apply allergen avoidance techniques. Whilst avoiding eating fish might be fairly easy, accidental exposure to the odour may occur by chance.
7. Vibrations (vibratory urticaria)
Another very rare form of physical urticaria is that caused by vibrations.
Researchers have found that these can trigger the release of inflammatory substances into the body causing hives and rashes.
Basic actions such as clapping, running, travelling or using a drill can all induce urticarial reactions. Most vibratory reactions last for less than an hour but might still cause feelings of self-consciousness and discomfort.
Avoidance of the trigger stimuli in such cases is sometimes possible, but not always.
Those who have responses to exercises such as running may instead need to consider low-impact activities; a doctor will be able to help you select an appropriate workout plan.
Diagnosis and treatment
By virtue of their less common status, many rare allergies will be more problematic to diagnose, but patients shouldn’t stop seeking help.
‘Gaining an allergy diagnosis is a complicated process and is better described as a journey.’ Holly explains. ‘It may involve several visits to the GP and a secondary care specialist such as an allergist or dermatologist who has the specialist knowledge to make a diagnosis.’
Is there anything those suspicious of an allergy can do to help the process? Holly suggests:
‘Keeping a symptom diary and reaction diary with potential triggers and supporting this with photographic evidence of skin rashes or hives may be a valuable tool in assisting your doctor.’
Most rare allergies will require an individual approach to treatment including a combination of medications and avoidance techniques. But how do commonplace antihistamines fare?
‘Second generation antihistamines that are long acting and non-sedating (that do not cause drowsiness or make people feel tired) that enable allergy sufferers to carry on with their normal daily activities and aid symptom control are recommended. Your GP or pharmacist will be able to recommend a type of antihistamine specific to your requirements.’