Is Alum Safe To Eat or Use?

Safety of Alum in Food and Household Products

Alum crystals may be natural deodorants, but that doesn't mean they are completely non-toxic.
Alum crystals may be natural deodorants, but that doesn't mean they are completely non-toxic. GARO/PHANIE / Getty Images

Question: Is Alum Safe?

Have you ever wondered if alum is safe to eat or safe to use as an underarm deodorant? Here's a look at what alum is and whether it's safe.

Answer: Alum Safety Depends on Multiple Factors

Any form of aluminum sulfate could be called "alum," including toxic versions of the chemical. However, the type of alum you find used for pickling and in deodorant is potassium alum, KAl(SO4)2·12H2O.

Sodium aluminum sulfate is a type of alum that is used in commercial baking powder.

Potassium alum has been used in maraschino cherries and pickles. The aluminum helps make the cell walls of fruits and vegetables sturdier, producing a crisp pickle or firm cherry. Although alum is approved as a food additive by the U.S. Food and Drug Administration, it is toxic in large doses. The current trend is to reduce reliance on chemicals to improve food texture. Alum may be used to soak some pickles, but it is no longer used in the final pickling solution.

Alum in deodorant may be absorbed across the skin into the bloodstream. Although it is deemed safe enough for this purpose by the Food and Drug Administration, there may be negative health consequences from continued exposure to the aluminum ions in the alum. Because some of the product is absorbed into the skin, one way to cut your exposure to the product is to apply it every other day, rather than every day.

Alum Health Concerns

All forms of alum can cause irritation of the skin and mucous membranes. Breathing alum can cause lung damage. Aluminum also may attack lung tissue. Because it's a salt, eating massive amounts of alum can make you sick. Usually ingesting alum will make you vomit, but if you could keep it down, the alum could upset the ionic equilibrium in your bloodstream, just like overdosing on any other electrolyte.

However, the primary concern with alum is longterm exposure to low levels of the chemical. Aluminum, from your diet or healthcare product, can cause degeneration of nervous system tissue. It is possible exposure to aluminum could lead to an increased risk of certain cancers, brain plaques or Alzheimer's Disease.

Alum Material Data Safety Sheets

If you are concerned about specific risks associated with alum, it's best to consult a Material Data Safety Sheet. You can search for these online. Here are some relevant MSDSs:

Potassium Alum MSDS
Sodium Alum MSDS
Aluminum MSDS


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Hawkes, Nigel (2006-04-20). "Alzheimers linked to aluminium pollution in tap water". The Times (London). Retrieved 2012-09-12.
Aluminium and Alzheimer's Disease, The Alzheimer's Society. Retrieved 11 September 2012.