urticaria

23 Jul

Urticaria, also known as Hives, is a reaction to different irritants that results in red, patchy, and itchy areas arising in the skin. It can be acute (short term) or chronic (long term) dependent on what causes the rash and how long it lasts for. The reaction occurs as high levels of histamine (the product released in allergic reactions and hay fever) are released into the body.

- The prevalence of short-term urticaria is approximately 12-23.5% [1]
- Patients between 20-40 have been found to be more frequently affected by urticaria [2]
- The global prevalence of urticaria in 2017 was 86 million people
- Females have a greater burden of disease (measures the impact of living with illness and dying prematurely) than men [3]
- Certain foods (eg. peanuts, eggs, nuts, shellfish)
- Medications (eg. penicillin)
- Insect stings/bites
- Condition exposure eg. pressure, heat, cold
- Latex exposure
- Blood transfusions
- Viral and bacterial infections
- Pet fur
- Pollen
- Certain plants (eg. poison oak, stinging nettle) [4]
Medical Students
- Cutaneous mast cells are central to the pathogenesis of urticaria.
- Mast cell degranulation releases preformed mediators such as:
  - Histamine
  - Tryptase
  - Cytokines
- Histamine acts on post-capillary venules and C-fiber nerve endings, leading to itching via the CNS.
- Skin biopsies from lesions show an early influx of:
  - Neutrophils
  - Eosinophils
  - Basophils
  - Undifferentiated T-cells
- In allergic urticaria, degranulation is triggered by IgE cross-linking on FcεRI receptors on mast cells/basophils.
- In autoimmune urticaria, autoantibodies against IgE or FcεRI activate mast cells and basophils to release histamine.
- Physical stimuli (e.g., pressure, cold) in inducible urticarias may also involve IgE and mast cells.
- Angioedema without wheals may be:
  - Mast cell-dependent or
  - Mast cell-independent (e.g., bradykinin-mediated).
- Clinicians must rule out hereditary angioedema (HAE) by:
  - Measuring C4 complement and C1 esterase inhibitor levels in fresh blood samples.
Patients
- Special immune cells in the skin called mast cells are responsible for most symptoms of urticaria.
- When activated, these mast cells release substances like:
  - Histamine (causes itching and swelling)
  - Tryptase
  - Cytokines
- These chemicals cause itching, redness, and swelling by affecting nerves and small blood vessels.
- In skin samples, doctors can see many immune cells rushing to the area, including different types of white blood cells.
- In allergic types of urticaria, certain proteins (called IgE antibodies) trigger mast cells to release histamine.
- In other forms, the body creates autoantibodies that wrongly attack its own cells, also triggering histamine release.
- Some types of urticaria are triggered by physical factors like pressure or cold.
- Angioedema (deep swelling, often of the lips or eyes) can happen with or without a rash.
- When it happens without a rash, it might be due to a different cause such as hereditary angioedema (HAE). [5]
- Exposure to certain conditions (eg. pollen, heat, UV, pressure, cholinergic- emotional trigger) [4,6]
- Elevated patches
- Itchiness
- Red coloured plaques
- Reddish- brown macules (spots)
- Spots with yellow/white colouration on darker skin [7]
- Clinical examination of the appearance as well as a history of urticaria
- Tests for the liver function for hepatitis and thyroid function for autoimmune urticaria
- Erythrocyte sedimentation rate to investigation an underlying condition
- Full blood count to invest the presence of infections
- Allergy testing using a skin prick or patch test or IgE tests for specific allergic triggers that cause urticaria
- Elimination of food or drugs as urticaria triggers
- Urine test for urinary tract infection or renal involvement
- Physical challenges to determine the origin of urticaria
- Cold-induced- ice placed on the arm
- Dermographism- lightly scratching the skin
- Aquagenic- placing a body part into the water
- Cholinergic- exercising the person to trigger heat from sweating
- Delayed- pressure- 15 pounds of weight can be placed on the person’s shoulders to determine wheals with a delay of 4-6 hours [6]
- Short-term (acute) sudden urticaria
- Long-term (chronic) sudden urticaria
- Physical urticaria caused by factors such as heat, pressure and water
- Drug exacerbation causing urticaria
- Insect bites
- Viral rash
- Atopic dermatitis/ allergic contact dermatitis- inflammation of the skin caused by allergens
- Irritant contact dermatitis- inflammation of the skin caused by irritants Eg. chemicals [8]
Medical Students
- Identify and manage triggers (e.g., allergens, infections, stress); advise on avoidance strategies.
- Trial discontinuation of possible causative medications (e.g., NSAIDs) for several weeks.
- Consider appropriate investigations for recurrent or persistent urticaria if no clear cause is identified.
- Use Urticaria Activity Score (UAS7) or symptom diaries to assess severity and frequency.
  - Mild urticaria with known triggers may resolve without treatment—reassure patients.
  - Treat with non-sedating antihistamines (cetirizine, fexofenadine, loratadine) for up to 6 weeks or longer.
  - For severe symptoms, add a short course of oral corticosteroids.
- Refer children <16 years needing corticosteroids to dermatology or paediatrics.
- If antihistamines are ineffective, consider:
  - Increasing the dose (up to 4x, under supervision),
  - Switching agents,
  - Adding leukotriene receptor antagonists (e.g., montelukast),
  - Using topical antipruritics (e.g., calamine lotion).
- Consider sedating antihistamines at night for sleep disturbance.
- Use CU-Q2oL (Chronic Urticaria Quality of Life Questionnaire) to assess impact.
- Refer to specialist care (dermatologist/immunologist) if:
  - Suspected vasculitic urticaria,
  - Angioedema without wheals, unresponsive to first-line therapy,
  - Acute severe urticaria (e.g., food/latex allergy),
  - Chronic inducible urticarias (e.g., cold, solar) difficult to manage.
- Consider clinical psychology referral for significant psychosocial impact.
Patients
- Try to identify and avoid triggers (e.g., certain foods, infections, medications).
- You may be advised to stop taking certain medications (like ibuprofen) for a few weeks.
- If the cause of your urticaria isn’t clear, your doctor may suggest blood tests or investigations.
- Keep a symptom diary to track how often and how bad your rashes or itching are.
  - Mild symptoms may go away on their own, especially if the cause is known and avoided.
  - You may be prescribed a non-drowsy antihistamine like cetirizine or loratadine.
  - If symptoms are severe, your doctor might suggest a short course of steroids alongside antihistamines.
- Children needing steroid treatment will usually be referred to a specialist.
- If standard antihistamines don’t help, your doctor might:
  - Increase the dose,
  - Try a different antihistamine,
  - Add another medicine that helps stop inflammation,
  - Suggest a cream or lotion to reduce itching.
- If itching affects your sleep, a nighttime antihistamine that makes you sleepy may be offered.
- Your doctor may ask about how urticaria affects your daily life and wellbeing.
- You may be referred to a specialist if:
  - Your hives are painful or don’t go away,
  - You have swelling (angioedema) without a rash that doesn’t improve,
  - You react severely to food, latex, or other triggers,
  - Your urticaria is difficult to manage, especially if caused by physical triggers like cold or sunlight.
- If urticaria causes stress, low mood, or social issues, a psychologist may be able to help. [9]
- Angioedema- swelling of the tissues
- Mental health complications such as stress and anxiety caused by presentation
- Anaphylaxis- a severe allergic reaction [10]
- There is a cure for urticaria
- Long term urticaria is an allergic reaction
- Urticaria is never severe
- Urticaria is contagious
- Avoidance of certain foods is necessary to manage urticaria
- Treatment for urticaria is lifelong [11,12]
- What lifestyle choices will help me manage symptoms of urticaria?
- How long will treatment take to be effective?
- How can you determine what triggers my urticaria?
- What can I do to prevent complications from arising
- Allergy and Asthma Network
- Allergy UK
- British Association of Dermatologists
[1] https://onlinelibrary.wiley.com/doi/full/10.1046/j.1398-9995.2003.00327.x
[2] https://academic.oup.com/bjd/article-abstract/138/4/635/6683018?redirectedFrom=fulltext&login=false
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9364256/
[4] https://acaai.org/allergies/allergic-conditions/skin-allergy/hives/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4954105/
[6] https://cks.nice.org.uk/topics/urticaria/background-information/causes-trigger-factors/
[7] https://www.msdmanuals.com/en-gb/professional/dermatologic-disorders/approach-to-the-dermatologic-patient/urticaria?query=hives
[8] https://bestpractice.bmj.com/topics/en-gb/210/differentials#diffCommon
[9] https://cks.nice.org.uk/topics/urticaria/management/managing-urticaria/
[10] https://www.nhsinform.scot/illnesses-and-conditions/skin-hair-and-nails/hives
[11] https://www.healthcentral.com/article/chronic-autoimmune-illnesses-linked-to-chronic-hives
[12] https://saikiaskin.care/top-10-myths-and-faqs-about-hives/