Food Challenges

Gold standard for diagnosis of a food allergy or intolerance. The suspect food is strictly excluded for a period, generally not less than 2 weeks, and then the food is re-introduced. Symptom control during this process should confirm or refute the diagnosis. The challenge is only considered complete once a normal age-appropriate portion of the food has been consumed.

In certain cases, food challenge is potentially more dangerous, and should only be done in a specialist setting with emergency support immediately available, and if there is a moderate to high risk of a severe reaction, intensive care support should be immediately available:

  • Where the initial reaction sounds severe (anaphylaxis or FPIES)
  • Where the patient has asthma

The challenge can be blinded if there is still doubt. Objective measures of symptoms/signs may be required. Eczema, wheeze, congestion, diarrhoea should all have resolved prior to doing the challenge, to avoid potential confusion.

The risk of causing a reaction should be weighed against the potential benefit of removing dietary restrictions and reducing fear/anxiety.

[EAACI food allergy diagnosis, Allergy 2014]

Honey in medicine

Contains a range of different sugars, aromatic oils, also pollens and bee proteins. Royal jelly and beeswax related, of course.

High fructose content can cause GI intolerance in some.

Allergic reactions can happen, often unrecognised, either to specific pollens (depending on what flowers the bees feed on) or bee proteins. IgE test for honey is available, but you may need to skin prick test with the specific honey if negative.

Honey eaten all year round is rumoured to prevent hay fever symptoms because of the pollens it contains, but this has not been proven, although it’s a nice idea related to immunotherapy. Depends on getting the right pollens of course – bees don’t like grass and birch flowers, probably. In some it may just trigger allergy symptoms.

Cross reaction between honey and bee venom is reported, not surprisingly, but not automatic.

Plant toxins can be present in sufficient quantities in honey to cause poisoning eg rhododendrons (some species).

Botulism reported in infants – failure to thrive, hypotonia, cranial nerve palsies. Clostridium and other bacteria cannot grow in honey due to the high sugar content, but spores can be present. So advice is not to give honey to infants.

Coagulation

Extrinsic pathway triggered by tissue factor on cells outside blood vessels.

Intrinsic pathway triggered by subendothelial surfaces activating factor XII, then XI, then IX.  IX and VIII combination with calcium and platelet membrane phospholipids activates X.

Common pathway then continues, with X combining with V, platelet membrane phospholipids and calcium to convert prothrombin to thrombin.

Thrombin converts fibrinogen to fibrin, to form thrombus.  Factor XIII stabilises clot.

Issues:

  • Vitamin K deficiency: 1:1200 breast fed (low levels), 1: 8500 formula fed. Preventable with single IM dose of Vitamin K. Can present up to 6 months later though typically 3 months.
  • Vitamin K may be affected in babies by maternal medicines eg anti-epileptics, or by liver disease.
  • Disseminated intravascular coagulation especially sepsis. Platelets fall too.
  • Haemophilia
  • Haemophagocytic syndrome (anaemia and other cell lines affected)
  • Thrombophilia

Radial dysplasia

Spectrum of congenital abnormalities of hand and forearm, from hypoplastic or absent thumb, to short arm with deviated, clubbed hand.

Commonly part of a congenital syndrome, so refer to a clinical geneticist.

  • VACTERL Association,
  • VATER syndrome,
  • Holt-Oram syndrome ( association of cardiopulmonary and limb defects),
  • TAR syndrome (thrombocytopenia-absent radius),
  • Fanconi anaemia.  

Investigations

  • Spine x-rays,
  • renal ultrasound,
  • complete blood count,
  • echocardiography

Renal tubular acidosis

Leaky tubules, shedding bicarbonate plus other things, leading to acidosis.

  • Type 1 is distal tubule, which does most of the reabsorbing.
  • Type 2 is proximal tubule, so similar but less severe.
  • Type 3 probably just a mixture of types 1 and 2!
  • Type 4 have high rather than low potassium, so clearly not a leakage issue. Related to aldosterone ineffectiveness.

Types 1 and 2 can present with growth failure, else the effects of hypokalaemia (profound muscle weakness) and acidosis (abdominal pain). Type 1 leads to progressive kidney disease, with the associated bone disease (rickets). May also end up with stones. Associated with sickle cell, Ehlers Danlos.

Type 2 usually Fanconi syndrome so leakage of amino acids, phosphate etc. Can be caused by Cystinosis, Wilson’s, hereditary fructose intolerance, poisoning.

Type 4 often related to drugs, but also Addison’s, urinary tract obstruction.

Allergy Plans

People with a food allergy or who have had a previous severe reaction (anaphylaxis) to anything should have a written plan, describing clearly what they should do if they have a reaction.  This should be completed by your doctor or allergy professional.

This plan should be reviewed every year, to check that the names and doses of medicines are correct, and that it includes a blue inhaler if you have one.

The British Society for Allergy and Clinical Immunology (BSACI) and Royal College of Paediatrics and Child Health have published an allergy plan template that can be completed online and printed, with different versions depending on whether you have been prescribed an adrenaline autoinjector, and which one you have.

Your allergy clinic may have their own version. The BSACI one has the advantages of being in colour, it also includes (in very small print) parental authorisation for a school to administer an autoinjector (technically not legally required of course, but might overcome hesitancy), and a comment about having autoinjector in hand luggage on a plan. It also includes a link to the Spare Pens in School website. But it doesn’t emphasize carrying your medication at all times, and doesn’t allow for a second dose of antihistamine unless you vomit the first one.

The plan should list the different signs and symptoms of a reaction, and make it clear which signs and symptoms should alert you to the possibility of a severe reaction.  It should then give clear advice on whether you can give medicine and wait for things to get better or whether you should be using your adrenaline autoinjector (if you have one) and phoning 999.

The plan should ideally stay with your allergy medicines and your child, wherever they go.  You may need copies for other people who help look after your child, for instance grandparents, child minders, nursery and school, after school care. Getting your plan laminated can help it stay legible!

Schools may also want to have a written document that details what extra precautions are necessary in the school environment or on school trips.

Allergy plans are also available from the Epipen and Jext websites, for families who have those adrenaline autoinjector devices.

Safe Food Skills for Allergy

  • Ask about ingredients of unfamiliar food
  • Declare allergy in restaurants, cafés, when ordering take away food (preferably to real person rather than app/website)
  • Inform family and friends about allergy
  • Don’t accept food if unclear what the ingredients are
  • Read ingredients labels #EveryLabelEveryTime
  • Consider the risk of items with “may contain” warnings
  • Appreciate risk of contamination of surfaces/utensils/hands
  • Carry allergy medicines and plan when out of home/school

Micropenis

In neonates and infants, the stretched penile length is at least 2cm in 97% of boys.

Micropenis describes a shorter penis than this, that is otherwise of normal form. Penis needs to be stretched out, and suprapubic fat pad pushed in.

Causes are hypogonadotrophic (Kallman’s syndrome, Laurence-Moon-Biedel-Bart, Prader-Willi) or hypogonadism (anorchia or testicular dysgenesis, Trisomy 21, Noonans, Klinefelter). May be part of more complex syndrome.

Differential is intersex, “buried penis” due to suprapubic fat pad (usually obese), chordee.

Neat trick is to modify a 10ml syringe by cutting off needle end and inserting plunger into cut end. Gives you scale and stretches penis!

[https://dx.doi.org/10.4274%2FJcrpe.1135]

Contact dermatitis

Type 4 delayed hypersensitivity seen to a range of things including:

  • Nickel (for example in jewellery, belt buckles, fastenings)
  • Limonene, found in many cleaning products and cosmetics
  • Sodium lauryl sulfate, found in cleaning products and cosmetics
  • Lanolin and other wool products

Mechanism is complicated as metals are clearly not proteins so not identified by HLA class 2 as happens in type 1 allergy. Presumably happens through toll like receptors.

Testing is by patch testing, done by dermatology.