Urticaria (Hives) and Angioedema in Children

00:01 In this lecture, we'll discuss allergic reactions including anaphylaxis, urticaria, angioedema and food allergy.

00:09 So there are generally 4 types of hypersensitivity reactions.

00:14 This is your basic science material.

00:16 Type 1 is IgE mediated and an example would be anaphylaxis.

00:21 Type 2 is IgG or IgM mediated antigen on a target cell and an example of that would be rheumatic heart disease.

00:30 Type 3 is when there are circulating antigen/antibody complexes.

00:35 An example of this type of reaction is for example serum sickness.

00:39 And a type 4 hypersensitive reaction is generally a T-cell mediated response such as poison ivy, or a PPD test, or milk protein allergy presenting as blood in the stool as an infant.

00:53 So, let's start with type 1 hypersensitivity reactions.

00:59 In general, these require exposure to a protein that's large enough to be an antigen.

01:05 So, the patient has an initial exposure to that antigen, and they produce an antigen-specific IgE.

01:12 That IgE now binds to a mast cell, and on a subsequent exposure to that antigen, they generally have a generalized mass cell degranulation resulting in a type 1 hypersensitivity reaction.

01:28 There are many things that can trigger such a reaction.

01:31 These include foods, especially food additives, legumes, tree nuts, seafood, eggs, dairy, shellfish, berries.

01:39 These are all very common.

01:41 In fact, among children who have type 1 hypersensitivity reactions to food about 85% of them are to food when we know what the allergen is.

01:53 Still, remember, at least a third of the time we have no idea what triggers the allergy.

01:58 Also, patients can be allergic to medications.

02:01 Probably penicillins and sulfas are the most common, but they could also be allergic to salicylates to certain vaccines or to anaesthetics.

02:10 Also patients can have environmental allergies.

02:14 Bee stings and wasp stings are particularly problematic.

02:18 Patients may be allergic to temperature changes to exercise, to latex.

02:22 Lots of different possibilities.

02:25 So, urticaria is our classic type 1 hypersensitivity reaction.

02:30 We also call it "hives".

02:32 These lesions will be anywhere from 1 mm to 10 cm large.

02:37 They can be huge or small.

02:38 These lesions are profoundly itchy, and they're stimulated by skin contact, which means the more you scratch them, the more they itch.

02:48 What you'll notice about them is that they sort of "come and go" even before your eyes.

02:53 You may walk in, see a patient with hives, and before you're done with your conversation, the one you were looking at on the leg is gone, and there's a new one on the arm.

03:02 They may be associated with angioedema, which is another type of type 1 hypersensitivity reaction.

03:10 What's key is that these are acute and generally short-lived.

03:14 Patients usually only have this reaction for maybe days to maybe a week out, from when they're first encountered that antigen, and had a response to it, which would be the second time they ecountered the antigen.

03:26 Alternatively, occasionally they can become chronic.

03:30 These are when hives last longer than 6 weeks.

03:33 This can really be problematic when it happens.

03:37 So, the diagnosis of urticaria is based on appearance.

03:41 This is a great picture.

03:42 Just remember they're sort of serpiginous, round with central clearing.

03:46 This is a classic hives reaction.

03:48 They're a little bit raised.

03:50 We're going to treat this with oral antihistamines.

03:54 That's our mainstay of therapy, basically diphenhydramine.

03:58 Patients may add H2 antagonists, such as famotidine, to the mix to try and limit the effect of the histamines.

04:06 This has a minimal benefit, but it's certainly isn't particularly harmful to be on famotidine for a few days while you're waiting for your hives to improve.

04:16 What's key is steroids are generally not helpful, so we do not routinely provide steroids to patients with urticaria.

04:23 So, angioedema, I mentioned this earlier.

04:28 This is sort of like hives gone wild.

04:30 This is a general localized swelling that happens in an area, often on the face.

04:37 It can happen around the eyes.

04:38 It can happen on the lips, the mouth, or the tongue.

04:42 It may happen on the genitalia, or the extremeties, or even in the bowel wall causing either bowel discomfort or nausea, vomiting, or more systemic symptoms.

04:54 What's key though and where we would worry, is when this involves the lips, the mouth, and the tongue, because we worry about the patency of the airway.

05:02 Sometimes, the swelling can get so bad, the patient may have trouble breathing.

05:06 This is an allergic reaction -- or it can be inherited.

05:12 There are rare diseases such hereditary angioedema where patients can get this randomly throughout their lives.

05:20 In specific, we sometimes see this to certain medications and the classic one is the ACE inhibitor.

05:27 Any patient on an ACE inhibitor, who gets this reaction, it's an emergency because we may lose that airway.

05:34 Additionally, NSAIDS can do this and calcium channel blockers can rarely do this.

05:40 The classic one is ACE inhibitors.

05:43 So, what do we if we have a patient with angioedema? Well, first, remove the offending agent.

05:49 Get them off the drug that's caused it or whatever has caused it, get them out of it, get it out of them.

05:53 Then we're going to treat it similarly to hives.

05:56 So, we're going to give the benadryl we talked about.

05:59 We'll probably do that around the clock.

06:01 We may add Zantac.

06:03 If the airway is involved, we generally would admit these patients to the hospital to make sure that that airway isn't goint to become compromised.

06:11 If the airway is obstructed, we immediately give epinephrine and provide immediate airway stabilization and airway support.

06:19 It may require intubation and in very rare cases, an actual tracheostomy, if you're incapable of getting an intubation.

06:27 Sometimes a layringoscopic intubation is needed.