Allergy and the Skin Flashcards
Skin symptoms in IgE mediated food allergy
Pruritus
Erythema
Acute urticaria
Acute angioedema
GI symptoms in IgE mediated food allergy
Angioedema Oral pruritis Nausea Colicky abdominal pain Vomiting Diarrhoea
Respiratory tract symptoms in IgE mediated food allergy
URT - nasal itching, sneezing, rhinorrhoea, congestion
LRT - cough, chest tightness, wheezing, SOB
Skin symptoms of non-IgE mediated food allergy
Pruritus
Erythema
Atopic eczema
GI symptoms of non-IgE mediated food allergy
GORD Loose or frequent stools Blood and/or mucus in stools Abdominal pain Infantile colic Food refusal or aversion Constipation Perianal redness Pallor and tiredness Faltering growth
Allergy focused clinical history
History of atopic disease (personal and family)
Details of food avoided and why
Presenting symptoms and other symptoms that may be associated with food allergy
Cultural and religious factors that can affect an individual’s diet
Who has raised the concern and suspects food allergy?
What caused the allergen to be suspected?
Child feeding history incl. age of weaning and whether breast/formula fed
Details of previous treatment
Any response to elimination and reintroduction of foods
Questions relating to presenting symptoms and other symptoms that may be associated with food allergy
Age at first onset
Speed of onset
Duration, severity and frequency
Setting of reaction (school/home)
Reproducibility of symptoms on repeated exposure
What food and how much exposure to it causes a reaction
Urticaria features
Erythema with well-defined edge, smooth surface and can be treated with antihistamines
Eczema features
Ill-defined erythema with a scaly surface that can be treated with topical steroids and emollients
3 step plan for acute allergic reaction
1 = at first sign of reaction, give chlorophenamine (antihistamine) 2 = if allergic reaction does not resolve or gets worse over the next 30 minutes, seek urgent medical help and give prednisolone 1-2mg/kg 3 = if becomes blue or collapses, give adrenaline IM and dial 999
Diagnosis of food allergy
Clinical history very important
Specific IgE
Skin prick testing
Food challenge - gold standard
Specific IgE testing in the diagnosis of food allergy
Blood sample is taken and tested in lab. Measures level of IgE in the blood sample that can react to suspected allergen
Why is specific IgE testing not totally reliable?
The level of IgE in the blood does not correlate to the severity of food allergy
Skin prick testing in the diagnosis of food allergy
Small amount of suspected allergen is put onto skin and a small needle is used to push a small amount into the dermis. If allergy is present then a wheal will be seen
There must be a negative and positive control - negative = water, positive = histamine
Most common food allergens
Cow's milk Chicken egg Soya Tree nuts Fish Shellfish Peanuts Wheat
Types of food intolerance
Intolerance to unknown mechanisms
Pharmacological intolerance
Enzymatic intolerance
What is pharmacologic intolerance?
Intolerance to naturally occurring substances in food
Example of an intolerance to unknown mechanisms
To food additives
Examples of pharmacological intolerance
Histamine, salicylates, caffeine, theobromine
Example of enzymatic intolerance
Lactose intolerance
GI symptoms in mild to moderate non-IgE mediated cow’s milk allergy
Vomiting Reflux Unsettled Loose stools Constipation Abdominal discomfort Blood or mucous in stools
Skin symptoms in mild to moderate non-IgE mediated cow’s milk allergy
Pruritus
Erythema
Eczema
When will a reaction occur in mild to moderate non-IgE mediated cow’s milk allergy?
2-72 hours after ingestion of cow’s milk protein. Usually seen in formula fed babies at onset of formula feeding
GI symptoms in IgE mediated cow’s milk allergy
Vomiting
Diarrhoea
Abdominal pain
Skin symptoms in IgE mediated cow’s milk allergy
Acute pruritus
Urticaria
Angioedema
Acute flaring of dermatitis
Respiratory symptoms in IgE mediated cow’s milk allergy
Acute rhinitis
Conjunctivitis
Anaphylaxis if severe
When will a reaction occur in IgE mediated cow’s milk allergy?
Within minutes of ingestion of cow’s milk protein
How long should a cow’s milk free diet be followed for after the diagnosis of cow’s milk allergy?
For 9-12 months, at least 6 months
Extensively hydrolysed formula
Contain cow’s milk proteins that have been broken down into very short pieces and therefore do not trigger an allergic reaction
Why are rice milks not recommended for children <5 years
Due to increased arsenic content
Comfort milks
Milks with lower lactose content and are partially hydrolysed, making them easier to digest
What are comfort milks marketed for?
Management of colic
Anti-reflux milks
Milks containing a feed thickener with the aim of helping them stay in the stomach
Cause of pellagra
Vitamin B3 deficiency
What foods can you get vitamin B3 from?
Meat
Fish
Eggs
Fortified cereal and grains
Clinical features of pellagra
3 Ds: Dermatitis Diarrhoea Delirium/Dementia (can also lead to Death if untreated)
What is pellagra characterised by?
Photosensitive dermatitis affecting regions of the skin exposed to sunlight, heat and friction
Routes of exposure in type I allergy
Skin contact (animal dander, latex)
Inhalation (pollen, house dust mite)
Ingestion (nuts, seafood)
Injection (bee sting, medication)
Clinical presentation of type I allergy
Urticaria
Angioedema
Wheezing/asthma
Anaphylaxis
Angioedema
Localised swelling of subcutaneous tissue or mucous membranes
Non-pitting oedema
Management of type I allergy
Allergen avoidance
Antihistamines as first line
Anti-inflammatory (corticosteroid) as second line
Adrenaline injector (for anaphylaxis) third line or first line if signs of anaphylaxis
Sodium cromoglycate to block mast cell activation
Immunotherapy
Medical alert bracelet
Information and education
Dose of adrenaline injector for children and adults
Children = 150 micrograms Adults = 300 micrograms
Describe the process of patch testing
Allergens prepared on Finn chambers Finn chambers applied on back Remove after 48 hours Readings at 48 and 96 hours Specificity and sensitivity 70-80%
What causes irritant contact dermatitis?
Contact with agents that abrade, irritate and traumatise the skin directly
Examples of irritant contact dermatitis
Nappy rash and lip lick dermatitis
Conditions associated with endogenous dermatitis
Atopic eczema
Psoriasis
Management of dermatitis
Allergen/irritant avoidance/minimisation Emollients Topical steroids UV phototherapy Immunosuppressants
