• Laura Chaparro, science journalist

    Is the aluminium in deodorants safe?

    23 Dec

    Deodorants and antiperspirants have become indispensable in the daily hygiene of both men and women. How do components like aluminium chlorohydrate and alum stone (potassium alum) act to eliminate the odours caused by sweat?


    Aluminium chlorohydrate essentially reduces perspiration by plugging the pores of the skin with astringent salts that make it difficult for the odour-causing bacteria to multiply. Alum stone, on the other hand, exerts a powerful bactericidal action but, since the pores are not obstructed, the skin perspires as normal. 
    Our growing preoccupation with personal hygiene goes hand in hand with an interest in knowing how aluminium affects our body. Aluminium is present in the earth’s crust and in many products of daily use, such as saucepans, frying pans, soft drink cans, aluminium foil, food products, aspirins, antacids, water treatment agents, additives and cosmetics.


    How much aluminium do we absorb?
    A report by the US Agency for Toxic Substances and the Disease Registry (ATSDR) indicates that “everyone is exposed to low levels of aluminium from food, air, water and soil.” Our body eliminates aluminium naturally through the urine or the faeces. The European Authority of Food Safety (EFSA) recommends a tolerable weekly intake of 1 milligram of aluminium per kilogram of body weight.
    The ATSDR indicates that small quantities of aluminium are not detrimental to health. However, as happens with other potentially harmful substances, the situation is different when exposure is greater, as with workers who inhale large amounts of aluminium dust.


    An unproven link
    What remains unclear is the link between aluminium and Alzheimer disease. The first links between aluminium and neurodegenerative diseases were established in the 1960s when it was found that the metal accumulates in dementia-susceptible neuronal foci.
    A recent study by the University of British Columbia (Canada) analysed the possible links between Alzheimer and aluminium; although there was no evidence of a direct link, it was concluded that small doses cause neurotoxicity. According to the same study, over a lifetime small quantities of aluminium gradually accumulate in certain brain tissues.
    In Spain, the Revista Española de Salud Pública published a review of studies on the link between aluminium and Alzheimer disease. The conclusion was that, although a significant number of studies linked aluminium exposure and brain damage, a causal relationship with Alzheimer disease could not be definitively established on the basis of the existing evidence. However, the same review recommended reducing exposure to aluminium and controlling its use in foods and medicines and in workplaces. This recommendation has been endorsed by University of Kentucky research, which indicates that studies to date have not resolved the controversy.


    Safe dose
    Few doubts exist regarding aluminium doses in deodorants and antiperspirants, as these are not sufficiently high to represent a hazard. Research by the Purdue University and Penn State Altoona University (USA) has demonstrated that, in a single application in each underarm, the skin absorbs about 4 micrograms (a millionth part of a gram) of aluminium chlorohydrate, representing a mere 2.5% of the aluminium absorbed by the gut in food. The authors concluded that “one-time use of ACH applied to the skin is not a significant contribution to the body burden of aluminium”.



    Scientific American