Hives- What are they, When to worry

Hives- What are they, When to worry

Hives are a paradox with a happy ending.  Typically harmless, and more treatable than nearly any other rash, hives cause a tremendous level of concern.

The concern is based on the association of hives with a far more serious condition: a very severe form of allergic reaction called anaphylaxis.   In anaphylaxis, not only does the person have hives, but they develop very dangerous levels of trouble breathing and even drop blood pressure.

Even though nearly everyone with anaphylaxis has hives, almost nobody with hives has anaphylaxis.
How can this be?   Because millions of people, including millions of children have hives, but far, far fewer people actually ever experience anaphylaxis, fortunately.

What are Hives?

Hives are a rash caused by the release of a chemical called histamine.  The word hives has an unknown origin, the main guess is that it comes from a very old Scot word for rash.  The other name for hives is the very medical term for the rash, urticaria, which comes for a Latin word meaning burn.

Whatever the origin of the word, hives are a very distinctive rash that has these elements:

  • The appearance is described as welts.  Specifically hives, or welts, are a patch of skin that is raised or swollen, typically a pale red or even pink in color, and often with a central area that is pale or even whitish
  • Itch.  This rash is one of the itchiest known, for good reasons which we will note below.
  • It shifts.  Described medically as evanescent, the pattern and location of the hives moves over time.  In an hour entirely different parts of the skin can show the rash.  Where it was is now normal, and where it wasn't now has hives.
  • Antihistamine clears it up.  Most hives respond to use of benadryl, claritin, or other antihistamines.  More than any other rash, one dose of a medicine can make them vanish.
All these features come from the basic cause of hives.  As noted above, hives are almost always the result of cells in the skin releasing a particular chemical- histamine.   Histamine is a chemical found in a type of cell that populates all our skin, the mast cell.  Histamine, once released, makes all the capillaries around it leaky.  This is designed to allow elements in the blood stream to flood into an area that needs help.   But if a big pulse of histamine floods a patch of skin, the blood vessels in that patch get very leaky, fluid accumulates, and the skin develops the swollen, pale red, whitish look of hives.  Histamine is also a very powerful stimulant of itch.  It turns on the itch signal in nerves in the skin.  Finally, histamine usually once released is quickly cleared, so the release is like a flowing wash of histamine, it comes and it goes.  Releases of histamine can happen wherever there is skin.

These properties of histamine release easily explain all the features we see in hives:
  • The property of histamine to make local blood vessels leaky explains the swollen appearance
  • It's ability to cause itch nerves to fire explains the intense itch
  • The fact that histamine is like a wash explains why hives seem to appear and vanish so quickly, to move around the body.
  • And the fact that hives are due entirely to histamine release explains why antihistamines work so well.
What Makes Hives Happen?
Most people think hives are mainly the result of allergic reactions, but this is not true.  The most common reason hives appear is viral infections.  For some reason, having viruses growing in you often leads to histamine release, and so, hives.  Kids with colds and flus often get hives. 

At the same time, hives are of course a common experience of those with allergies.  This makes sense since the classic allergic reaction almost always includes the release of histamine.  It's histamine, along with other like compounds, that makes our noses run, our eyes itch, and our lungs wheeze and cough when an allergic reaction hits.  So it's no mystery that with all that histamine released in an allergic reaction, that hives appear, too.

When to Worry?
If hives appear and no change in breathing is seen, there is nothing to worry about at that time.
Hives are always harmless, it's other types of reaction that are potentially dangerous.
This bears emphasizing, if someone develops hives and their breathing is fine, the hives themselves are 100% harmless.  They do cause discomfort, they itch like crazy, but itch is not dangerous, it causes no threat to any important function of the body.
Further, hives typically respond well to antihistamine, so not only are they safe, but they can often be cleared away with use of a very safe medicine.

If when hives appear breathing starts to be labored, then it is time to worry and take emergency action.
Of course, whenever breathing begins to be hard, that is cause for concern.
In the setting of hives, any sense that your child is starting to struggle to breathe raises concern for an allergic reaction that is going to cause serious lung reactions.   This is quite different than a rash, or skin reaction.  As noted, skin reactions are harmless if unpleasant, but lung reactions can be dangerous.
The first step when you see hives with trouble breathing is to give a teaspoon of benadryl.  If the trouble breathing appears to be worrisome, call 9-1-1.  If the trouble breathing is very mild and not at all worrisome, you then have time to call us.

How to use Benadryl
Benadryl, or diphenhydramine (di-phen-hy-dra-mene) is a very, very safe, old medicine, a basic antihistamine.  It comes in liquid and pills, there is no child version.  So it's the dose that makes it right.  
For mild reactions and rashes, like just hives, the dose for young children is 6.25 mg and for older children 12.5mg.
For breathing issues, the dose for young children is 25 mg and for older children 50 mg.
The liquid comes as 12.5 mg/tsp, and the pills are 25 mg or 50 mg each.
The main side effect is tiredness, but in young children it can cause agitation.

1.  Hives are a particular type of rash, notable for their appearance as welts, intense itch, ability to come and go rapidly, response to antihistamine by clearing and itch ending.
2.  Hives are most commonly caused by viruses, but of course are also seen in allergic reactions.
3.  Hives by themselves are harmless.  If there is no accompanying trouble breathing or threat of trouble breathing, there is no danger.
4.  It is only in the setting of a very serious allergic reaction with struggle breathing that hives are of concern.  If trouble breathing is present in any situation, seeking medical help is very important and urgent.
5.  The use of an antihistamine can help clear away hives and restore comfort.

To your health,
Dr. Lavin 

*Disclaimer* The comments contained in this electronic source of information do not constitute and are not designed to imply that they constitute any form of individual medical advice. The information provided is purely for informational purposes only and not relevant to any person's particular medical condition or situation. If you have any medical concerns about yourself or your family please contact your physician immediately. In order to provide our patients the best uninfluenced information that science has to offer,we do not accept samples of drugs, advertising tchotchkes, money, food, or any item from outside vendors.

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