Weird allergy question: why would a rash only ever appear on one finger of my left hand?
May 24, 2010 3:30 PM   Subscribe

Weird allergy question: why would a rash only ever appear on one finger of my left hand?

I have adult-onset food sensitivities (family history finally catching up with me) and have a weird problem. When I eat something I shouldn't eat, I get an itchy, blistery rash on the inside of the middle finger on my left hand. The rash never appears anywhere else on my body and always directly follows ingestion of anything with wheat and corn. It has been a very consistent response and I joke with my doctor that I can always tell how clan my eating is by looking at this finger like a thermometer.

I have seen an allergist about this. I tested positive on a RAST test to corn allergy and negative to wheat allergy (a celiac panel was also negative, although he says I might still be sensitive). Generally, I avoid these foods and the doctor does not seem terribly concerned about the rash ('if it bothers you, don't eat it' was one answer, and 'I wouldn't worry about a little rash like that' was another). But he was unable to explain why an allergic rash would be a) so localized to such a small spot and b) why that SPECIFIC spot.

As I said, I am not in harm's way here, really, and you are not my doctor etc. But I am just curious about what's going on here. Is this one of those 'life is strange' type of things, or is there a reason why an allergic rash would appear on that specific spot and no other?
posted by JoannaC to Health & Fitness (10 answers total) 1 user marked this as a favorite
Just want to say I don't know but this happens to me too. I have some sort of sun senitivity/allergy [doctors say "stay out of the sun" and then "put hydrocortisone on it" when I get a rash] and unless I'm really overdoing it, the only real indicator of it is a puffy/blistery rash on the outside of my index finger of my right hand. If I stay in the sun, this progresses to be a rash on my other fingers and my elbows and knees and sometimes my chest, but it rarely gets this far. My doctor did not find this a particularly interesting aspect of the whole deal and didn't know why it was happening when I asked him.
posted by jessamyn at 3:40 PM on May 24, 2010

Do you ever wear a ring on that finger? I have a ring that used to cause some irritation until I wised up and coated the inside of the ring with clear nail polish. I have some food allergies that cause my hands to break out, but the only finger that ever gets the allergic rash is that finger I used to wear the ring on, even though I haven't had a rash due to the ring itself in years.
posted by adiabat at 3:55 PM on May 24, 2010

I get that rash, predominantly along the thumb side of my right index finger (datapoint: right-handed, no ring) but on really bad days it'll creep all the way around my cuticle.

Cortisone usually settles it down. I wonder on occasion whether it's a fungus, but occasional tries using Tinactin don't seem to be any more effective than the cortisone.
posted by Lyn Never at 4:09 PM on May 24, 2010

I used to get this exact same thing on my right hand, but I couldn't really pinpoint what brought on the relapses, so to speak. The rash was always in the same exact place - where I had been badly bitten by a spider when I was about 14.

Oddly enough, it hasn't happened since I has my doctor do that bee venom desensitization thing. (oddly because it was definitely a spider and not a bee.)

Anyway. Have you ever been stung/bitten by some ghastly invertebrate in the general area of the rash's recurrence, previous to the first onset of the rash? (Please say yes so I am not the only weirdo.)
posted by elizardbits at 4:38 PM on May 24, 2010

Yeah, I think different areas of the body can get oddly sensitized to allergens.

I tend to have more "hay fever" in springs after I've had a particularly bad cold or flu.
posted by gjc at 4:48 PM on May 24, 2010

Another "dunno but" response here: Mr. Corpse gets the same one-finger rash, but on each hand. I believe that taking Benadryl takes care of it. No doctor has been particularly interested in it, or seen it as a sign of anything worth caring about.
posted by The corpse in the library at 5:02 PM on May 24, 2010

Oral Allergy Syndrome (OAS) is an allergy that localizes to a particular part of the body.

Also, my mate has a very severe allergy to poison oak. Whenever she so much as whiffs a brush fire in her childhood landscape, she breaks out in the places that were worst affected in her very first exposure.

In your case, with a corn allergy, I'd attribute the breakout on your middle finger to the fact that rubber gloves and finger cots are often powdered with corn starch.
posted by jamjam at 5:46 PM on May 24, 2010

Response by poster: Nope, no ring or anything like that. I did used to get a rash on the *pad* of that finger, and my doctor always thought it was a reaction to either the paper in my office (I used to work in admin) or the metal in my keys---those were the only two things I would touch only with those fingers. His verdict on the finger rash is a) that it is definitely an allergic rash, yersirree b) since it occurs after eating certain foods, is probably related c) is not very deadly or serious so I shouldn't worry about it and d) I am an allergic sort of person so I should just shrug and accept that these things will tend to happen to me.

Which is all fine :) Whatever :) I was just curious why it seemed that rash would be so localized and to such an odd spot. Glad I am not the only one...
posted by JoannaC at 5:52 PM on May 24, 2010

Oh, as an additional datapoint, I also get the ring-rash adiabat talks about, but it's not the same. Because I am substantially fatter than I was when I got married, I wear a series of ridiculous cheap cubic zirconia rings in place of my real tiny white gold wedding band. If the base of those rings is nickel, I get a very eczema-type rash when the thin layer of rhodium wears off, which I can stave off for a while with nail polish, but if it touches me the very red scaly non-blistery itchy rash busts out in hours and lasts for days with hydrocortisone. If the base is copper, it turns green but no rash. (If I wear nickel-post earrings, a similar horrible thing happens to my earlobes. I only wear titanium, surgical steel, or niobium in my nose, so no data points there.) Definitely not the same rash.

What happens on my index finger is not at all red, with the tiny blisters and eventually very tough skin, sometimes peeling. I haven't actually had the blisters in several years, but I will get the tough peeling with a little itching on occasion.

I think it must be environmental in some way, and I'm pretty sure stress plays a part.
posted by Lyn Never at 6:38 PM on May 24, 2010

I have Eczema, but only on my left hand. The difference between the two hands is striking - so I guess it's not all that uncommon to have unbalanced allergic reactions, perhaps?
posted by alex_skazat at 10:25 PM on May 24, 2010

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