Variation in Susceptibility of the Skin
Every worker who has worked with mustard gas has noticed that some individuals are much more susceptible to skin burns from this substance than are others. Marshall made a study of 1282 men at Edgewood Arsenal, using a 1 per cent and a 0.01 per cent solution of mustard gas in paraffin oil. A small drop of these solutions was applied to the skin of the forearm of the subject and the arm allowed to remain uncovered for about 10 minutes. The presence or absence of a positive reaction is indicated by the appearance or absence of erythema 24 hours later. The results were as follows:
| 1% | 0.01% | % of Total |
|---|---|---|
| Positive | Positive | 3.3 |
| Positive | Negative | 55.3 |
| Negative | Negative | 41.4 |
The test made on 84 negroes gave the following results:
| 1% | 0.01% | % of Total |
|---|---|---|
| Positive | Positive | 0.0 |
| Positive | Negative | 15.0 |
| Negative | Negative | 78.0 |
| Questionable | Negative | 7.0 |
“It is seen from the above tables that negroes as a race, have a much more resistant skin than white men. No negro of the 84 examined reacted to the 0.1 per cent solution, and of course none would react to a more dilute one. About 10 per cent of white men react to the 0.1 per cent solution, while 2 to 3 per cent react to the 0.01 per cent solution or are hypersensitive. About 78 per cent of the negroes fail to react to the 1 per cent solution, while only 20 to 40 per cent of the white race do not show a reaction.”
Fig. 37.
The same individual may also show variations in susceptibility and this has also been studied by Marshall.
“The effect of exercise and sweating was investigated. A number of individuals were given vapor burns (one to five minutes exposure) and then exercised until in a profuse sweat, and then the same exposure to vapors made. In all cases the burn produced after exercising was more severe. Sweating produced by having the subjects place their feet in hot water, produced the same increase in susceptibility. That the moisture on the skin produced by sweating is at least partly, if not entirely, responsible for the increased susceptibility, was shown in the following way: An area of the forearm was kept moist for a few minutes with wet cotton. The sponge was then removed and two vapor tests made, one over the moist area and one over normal, dry skin. In all cases the moist burn was the more severe, in one, producing a blister where the control did not.
“The skin of different areas of the body is undoubtedly somewhat different in its susceptibility. All our tests have been applied to the forearm. The hands are considerably more resistant than the forearm. Tests made by the oil method on the forearm, chest, and back, however, indicate very little difference in susceptibility of these areas. The skin in the neighborhood of old burns has been shown to be more susceptible.
“In general, the same individual does not become more susceptible to skin burns from continued exposure to the vapor. The great number of tests which have been made on the same individual at different times and under the same conditions, indicate a remarkable constancy in reaction. A series of men who were tested at various times during a period of four months, revealed slight changes from time to time in some of the men. No man who originally reacted to only the 1 per cent solution ever reacted to the 0.01, and likewise, no man who originally reacted to the 0.01 ever failed to react to the 0.1 per cent.
“Susceptibility of skin of animals. The paraffin oil test was used on a number of animals and indicated that differences in susceptibility exist in different species and in different individuals of the same species.”
| Species | Number Tested | Percentage Positive to | ||
|---|---|---|---|---|
| 1 Per Cent | 0.1 Per Cent | 0.01 Per Cent | ||
| Horse | 1 | 100 | 100 | 100 |
| Dog | 91 | 83 | 35 | 0 |
| Goat | 11 | 55 | 36 | 0 |
| Rat | 10 | 30 | 20 | 0 |
| Mouse | 7 | 70 | 14 | 0 |
| Rabbit | 2 | 100 | 0 | 0 |
| Guinea-pig | 12 | 33 | 0 | 0 |
| Monkey | 9 | 22 | 0 | 0 |
The horse appears to be the most sensitive and the monkey and guinea-pig the most resistant species, while the dog would seem to have a sensitivity as near man as any of the species studied. No animal has yet been found which will give a blister from the application of mustard gas.
Smith, Clowes and Marshall[22] have studied the mechanism of absorption by the skin. They find that it is quite evident that the mustard gas is at first rapidly taken up by some element on, or adjacent to, the surface of the skin and for two to three minutes it may be completely removed, and for ten to fifteen minutes partially removed by prolonged washing With an organic solvent, and to a lesser extent with soap and water.
An interesting phenomenon is observed when the untreated normal skin of one subject is impressed for five minutes upon an area of skin of another subject, which has been exposed previously to the vapors of mustard gas. Under these circumstances both donor and recipient may develop burns (due to the transposition of the poison from one skin to another), the intensity of which will vary according to the circumstances and the respective sensitiveness of the participants. The degree of transposition is most strikingly observed in the intensity of the burn on the donor’s arm. If two similar exposures are made on the arm of a sensitive man, and one of these burns is treated, so to speak, by contact for five minutes, with the skin of a resistant man, the treated burn will be markedly less severe than the control, in some cases being entirely prevented. If, however, the recipient is equally sensitive to or more sensitive than the donor, the burns on the latter will exhibit far less difference. Both treatments may be effected at once, using two recipients, one more, and the other less, resistant than the donor. In such a case the burn brought into contact with the more resistant skin will be the less severe.
Similarly, if a sensitive individual impresses his arm alternately against burns of the same concentration and exposure on a resistant and sensitive man, the recipient receives a more severe burn from the sensitive than from the resistant man.
This indicates that the skin of a resistant individual exhibits a greater affinity or capacity for mustard gas than that of a sensitive one. There is an actual partition of the gas between the two skins, with an evident tendency to establish an equilibrium in which the larger portion of the gas will remain in that skin which possesses the greater capacity for it.
“A tentative explanation of this phenomenon can be made as follows. A three phase system is involved—the air over the skin surface constitutes the outer phase; some fatty or keratinous elements of the skin, the central phase; and a cellular portion of the skin the inner phase. The central phase is rich in lipoids and poor in water, while the inner phase is rich in water and poor in lipoids. After exposure to the vapors of dichloroethylsulphide the central phase is the absorbing agent and tends to establish equilibrium with the other two phases. On account of the lipoid nature of the central phase no damage is produced here because the compound is not hydrolyzed. On its passage from the central to the inner phase hydrolysis takes place within the cell and damage results when a sufficient concentration of hydrochloric acid is attained. The outer phase is constantly being freed from vapor by diffusion and convection currents, so more and more can evaporate from the central phase. The susceptibility of an individual depends on the relative power of the central phase to hold the poison in an inactive form (not hydrolyzed) and prevent its entry into the inner phase at a sufficient velocity to result in the formation of a toxic concentration. We do not attempt to localize the central or inner phases with any definite structure of the skin. As mustard is known to penetrate the sebaceous ducts the fat here might form one phase and the epithelial lining another.”