Hypersensitivity Reactions (Long & Dry! Don't Read While Sleepy)

[ Follow-ups ] [ Post Follow-up ] [ The Henna Page Forum ] [ FAQ ]

Posted by SeeSee on June 30, 2000 at 14:34:16:

I am hoping to explain to you guys why there are differences in the type of "allergic" reactions to PPD and other sensitizing ingredients. What follows is summarized and quoted directly from "Immunology: A Short Course" by Eli Benjamini and Sidney Leskowitz; this is my text from various immunology courses and is as succinct as it gets. The study of immunology always did make my head spin....

There are four types of hypersensitivity reactions characterized:

Type I: Anaphylactic reactions, mediated by the antibodies that are also responsible for protecting you from parasite invasion (called IgE). Reactions are rapid, occurring within minutes after exposure.

Type II: Cytolytic/Cytotoxic reactions, the antigen binds to the surface of a cell and activates a separate arm of the immune system called the Complement Cascade.

Type III: Immune complex reactions happen when the foreign substance and antibodies form complexes in the tissue and the antibodies are called to the reaction site. The complement cascade is also involved. This reaction takes hours to set in.

Type IV: Cell-Mediated Immunity or Delayed Type Hypersensitivity. This is mediated by the T cells rather than the antibodies. The defining characteristic is local tissue damage. This type of reaction has a delayed onset and may occur within 1-2 days after challenge.

It looks to me like Types I and IV are the characteristic reactions to PPD exposure for those who are allergic. Types II and III are usually caused by repeated injection of substances, but I can't rule that out in the case of black dyes because they often find their way under the skin. The people who don't know any better are the ones who look for the Type I reaction, and when it doesn't happen, they assume everything has gone OK. An experienced allergist or immunologist can spot the difference between Type I and IV immune reactions but your GP can only store so much information is his/her head, so they are unsure about what they are seeing.

A Type I reaction will show on the surface what is called the "wheal and flare" reaction, an area of redness (erythema) and swelling (edema). Again it's very fast, it will take about 15 minutes to show up. Any of you who have had reactions to makeup or lotion will recognize it. The important thing about Type I which scares me a bit is sensitization.

"...once adequate exposure to the allergen has been acheived by repeated mucosal contact, ingestion or...injection, and IgE antibody has been produced, then an individual is considered to be sensitized. IgE antibody is made in small amounts....IgE molecules persist at the site for weeks..."

That means another exposure could make you feel even worse. Corticosteroids are the indicated treatment for Type I hypersensitivity, as well as antihistamines and in severe cases, epinephrine.

Type IV reactions are a bit tricker to explain...there is a longer period of sensitization (1-2 weeks, which may explain a lot of the stories we hear). It is the T cell's second exposure to the substance that causes the reaction. The gross appearance is redness and induration, or a raised thickening of the skin, reaching its peak at 24-48 hours after the initial reaction. A classic example of Type IV is poison ivy dermatitis, as well as nickel-chromium sensitivity from jewelry. "An additional pathologic component of contact sensitivity reactions in humans is the separation of epidermal cells, spongiosis, and blister formation." In other words you will be a flaky, pus-y mess!

I only wish I could find a driver for my scanner so I could scan the "lovely" colour plates showing each type of reaction taking place on some poor person's skin. Then there is the whole matter of the stuff finding its way into your lymph nodes and your organs, but that is another story.

I hope this clears things up, in your heads anyway....or at least I hope I haven't been blowing the dust off my books for nothing :^)

Follow Ups:

Thank you! Much appreciated! n/t Catherine Cartwright Jones 15:47:29 6/30/00 (0)

Post a Followup

Name:
E-Mail:

Subject:

Comments:
: I am hoping to explain to you guys why there are differences in the type of "allergic" reactions to PPD and other sensitizing ingredients. What follows is summarized and quoted directly from "Immunology: A Short Course" by Eli Benjamini and Sidney Leskowitz; this is my text from various immunology courses and is as succinct as it gets. The study of immunology always did make my head spin.... : There are four types of hypersensitivity reactions characterized: : Type I: Anaphylactic reactions, mediated by the antibodies that are also responsible for protecting you from parasite invasion (called IgE). Reactions are rapid, occurring within minutes after exposure. : Type II: Cytolytic/Cytotoxic reactions, the antigen binds to the surface of a cell and activates a separate arm of the immune system called the Complement Cascade. : Type III: Immune complex reactions happen when the foreign substance and antibodies form complexes in the tissue and the antibodies are called to the reaction site. The complement cascade is also involved. This reaction takes hours to set in. : Type IV: Cell-Mediated Immunity or Delayed Type Hypersensitivity. This is mediated by the T cells rather than the antibodies. The defining characteristic is local tissue damage. This type of reaction has a delayed onset and may occur within 1-2 days after challenge. : It looks to me like Types I and IV are the characteristic reactions to PPD exposure for those who are allergic. Types II and III are usually caused by repeated injection of substances, but I can't rule that out in the case of black dyes because they often find their way under the skin. The people who don't know any better are the ones who look for the Type I reaction, and when it doesn't happen, they assume everything has gone OK. An experienced allergist or immunologist can spot the difference between Type I and IV immune reactions but your GP can only store so much information is his/her head, so they are unsure about what they are seeing. : A Type I reaction will show on the surface what is called the "wheal and flare" reaction, an area of redness (erythema) and swelling (edema). Again it's very fast, it will take about 15 minutes to show up. Any of you who have had reactions to makeup or lotion will recognize it. The important thing about Type I which scares me a bit is sensitization. : "...once adequate exposure to the allergen has been acheived by repeated mucosal contact, ingestion or...injection, and IgE antibody has been produced, then an individual is considered to be sensitized. IgE antibody is made in small amounts....IgE molecules persist at the site for weeks..." : That means another exposure could make you feel even worse. Corticosteroids are the indicated treatment for Type I hypersensitivity, as well as antihistamines and in severe cases, epinephrine. : Type IV reactions are a bit tricker to explain...there is a longer period of sensitization (1-2 weeks, which may explain a lot of the stories we hear). It is the T cell's second exposure to the substance that causes the reaction. The gross appearance is redness and induration, or a raised thickening of the skin, reaching its peak at 24-48 hours after the initial reaction. A classic example of Type IV is poison ivy dermatitis, as well as nickel-chromium sensitivity from jewelry. "An additional pathologic component of contact sensitivity reactions in humans is the separation of epidermal cells, spongiosis, and blister formation." In other words you will be a flaky, pus-y mess! : I only wish I could find a driver for my scanner so I could scan the "lovely" colour plates showing each type of reaction taking place on some poor person's skin. Then there is the whole matter of the stuff finding its way into your lymph nodes and your organs, but that is another story. : I hope this clears things up, in your heads anyway....or at least I hope I haven't been blowing the dust off my books for nothing :^)

Optional Link URL:
Link Title:
Optional Image URL:

[ Follow-ups ] [ Post Follow-up ] [ The Henna Page Forum ] [ FAQ ]