There are two types of tattoos:
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Temporary tattoos - or henna tattoos.
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Permanent tattoos
Some advertise "semi-permanent tattoos", but it is doubtful whether it is feasible to put colour into the skin in a way that ensures that the colour only stays in the skin temporarily.
Henna tattoos
Temporary tattoos are also called black henna tattoos and these are painted directly onto the skin where they can remain for weeks.
Henna is a natural compound that produces a reddish-brown colour and is not in itself particularly allergenic. Henna color is a weak colourant and not very durable, and therefore temporary tattoo colours may be mixed with chemicals such as p-phenylenediamine (PPD) or related substances.
PPD and similar substances provide a nice black colour that is long-lasting, but the substances are highly allergenic and can cause lifelong allergy - both to tattoos and hair dye, where the substances are also used.
A study from the United Arab Emirates, where henna tattoos are popular, examined the contents of 25 henna products used for temporary tattoos and found that all contained PPD in concentrations between 0.4 per cent. and 29.5 percent (Ayesha Al-Suwaidi et al, 2010).
Permanent tattoos
It is very limited in what we know about the contents of tattoo colors.
However it’s been established that poorly soluble metals and metal mixtures have long been used for pigmentation. In recent years azo dyes have been more widely used as tattoo colour. Azo dyes in themselves are not toxic, but breakdown products of these colours can be carcinogenic and the colours can also be allergenic.
An Italian market analysis of metal content in tattoo ink from four different suppliers found metals such as aluminum, barium, copper and iron in larger quantities, as well as toxic metals such as cadmium, manganese and lead in small quantities. Also well-known allergens such as chrome, cobalt and nickel were found (Forte et al, 2009).
The Swedish Chemicals Agency surveyed 31 tattoo colours in various shades for harmful substances in 2010. The analysis found 20 aromatic amines (suspected carcinogens and allergens) and 14 metals. Only five of the 31 colours did not contain harmful substances.
A survey in 2009 conducted by the Swiss authorities, based on 152 samples of tattoo colours, found breakdown products of azo dyes and banned preservatives. The content in 62 samples (41 percent) was so harmful that the inks subsequently were banned. Furthermore, four of the samples - or three per cent - contaminated with bacteria (Bundesamt für Gesundtheit, 2009).
