Marzulli & Maibach (1973) reported that one of 5 sen-sitized volunteers reacted, under controlled conditions, to a challengeconcentration of 0.01% formaldehyde.
Patch-test studies with differentconcentrations of formaldehyde have shown that concentrations below0.05% rarely elicit an allergic reaction, even in sensitive individuals(Schulz, 1983).
Formaldehyde solution is a primary skin-sensitizing agent inducingallergic contact dermatitis (Type IV, T-cell mediated delayed hypersen-sitivity reaction); it may induce immunological contact urticaria(Type I, perhaps IgE mediated, immediate hypersensitivity reaction).
Patch tests performed with formaldehyde challenge concentrations of1% or less resulted in positive reactions in about 2% of all patientstested throughout the world; higher formaldehyde challenge concen-trations may be irritant (Anon., 1987).
There is no evidence in the literature of allergic reactivity ofthe mucous membranes of the eyes being caused by airborne formaldehydeor by formaldehyde solutions.
An allergic contact dermatitis reaction was provoked by a dose offormaldehyde of 0.25 µg/cm2 skin (challenge dose: 50 µg/cm2 with0.5% percutaneous penetration).
It has been shown that sensory irritation is the earliest humanreaction to formaldehyde, both in exposure studies and from complaintsabout indoor environments.
Since differences in indi-vidual reactions to formaldehyde are large in both the normal popu-lation and in hyperreactive and sensitized persons, it is difficult toestimate a concentration guaranteed not to produce negative reactionsin the general population.
8.7.1 Reactions with macromolecules Formaldehyde reacts readily with a variety of cellular nucleo-philes, including glutathione, forming adducts of varying stability(Feldman, 1973; Uotila & Koivusalo, 1974; McGhee & von Hippel, 1975).
In the exposure chamber, a bis-chloromethyl-ether (BCME) concentration of 0.5-2 µg/m3, due to the chemicalreaction of formaldehyde and hydrogen chloride, was estimated.
Allergic reactions to cosmetics containing formaldehyde as a pre-servative, especially shampoos, are unusual (Eckardt, 1966) and appearmostly among those who have been sensitized by occupational exposure.
Formaldehyde protects dietary-protein frommicrobial proteolysis in the rumen by reacting with free amino groupsin the protein, forming inter- and intramolecular methylene bridges(Siddons et al., 1982).
Formaldehyde also reacts with proteins (French & Edsall, 1945) andnucleic acids (Haselkorn & Doty, 1961; Lewin, 1966; Collins & Guild,1968; Feldman, 1973; Chaw et al., 1980); it reacts with single-strandDNA, but not with double-stranded DNA.
126.96.36.199 Systemic sensitization A case report has been described involving an anaphylactic shockreaction after accidental iv application of formaldehyde duringhaemodialysis treatment due to formaldehyde remaining in the equipmentafter disinfection.
4.2.1 Special products of degradation under specific conditions Highly carcinogenic bis(chloromethyl)ether can be produced by acondensation reaction between formaldehyde and hydrogen chloride(Thiess et al., 1973; Nelson, 1977; Albert et al., 1982; Sellakumar etal., 1985).