In looking for news articles mentioning barley water, I came across one saying that the Queen of England reportedly drank it everyday for her complexion. She really does have a remarkably good complexion for her age. Why would barley water help with skin? It was a traditional acne remedy in the British Isles; what component(s) of it might have been helping acne sufferers?
Acne is correlated with the presence of androgens. See this, this, and this. Apparently, androgens stimulate production of sebum, an oily secretion made in our skin pores. But there are substances that can partially inhibit production of androgens, such as the ones mentioned in this study abstract:
The effects of various calcium-channel blockers on androgen production by collagenase-dispersed mouse testicular interstitial cells were investigated. Cobalt caused a dose-dependent inhibition of the maximum rate of luteinizing hormone (LH)-stimulated androgen production without altering the concentration of LH required for half maximum stimulation (EC50). Nickel and manganese also inhibited LH-stimulated steroidogenesis but were less potent than cobalt. The major site at which cobalt treatment inhibited steroidogenesis was beyond cAMP formation and before 3 beta-hydroxysteroid dehydrogenase. This conclusion was based on the observation that cobalt inhibited dibutyryl cAMP-stimulated androgen production but did not affect protein synthesis and pregnenolone-supported androgen production. Androgen production was unaffected by the organic calcium-channel blockers verapamil and the (+) and (-) enantiomers of D600 at concentrations less than 0.1 mM. At a concentration of 0.1 mM the organic calcium-channel blockers inhibited LH- and dibutyryl cAMP-stimulated androgen production. Unlike cobalt, the organic calcium-channel blockers also inhibited pregnenolone-supported androgen production and reduced the rate of protein synthesis. Similarities between the effects of cobalt in the present study and previous reports of the effects of reduced extracellular calcium concentrations on androgen production suggest that cobalt inhibits androgen production as a result of its ability to block calcium influx. The calcium channels involved in the steroidogenic process appear, however, to be relatively insensitive to the organic calcium-channel blockers.
Two things jump out at me from these findings and conclusions:
1) Blocking influx of calcium might inhibit androgen production in some cells. Perhaps this would in part explain the recurring observations of high dairy intake and acne correlation. See this, this, this, this, this, this, and this. Dairy products are rich natural sources of calcium.
2) Cobalt, nickel, and manganese can inhibit androgen production. I have a nickel allergy, which is quite common, and a little research on cobalt quickly convinced me that I don't want to mess around with it as a supplement.
But manganese...now there's a lead. In small amounts (and small amounts only), manganese is necessary for our bodies. And it is highest in two foods: clove (the spice) and oats. Barley is also a very good source of manganese. Queen Elizabeth II, I salute you for your regular consumption of barley water, which I'm sure provides you with a steady supply of manganese.
Do you know how long oats have been used in skin care? One personal care website claims oats have been used for skin care for 4000 years. The skin and hair care company Aveeno takes its name from the Latin name for oats, avena sativa, and centers its products on oats.
Cloves don't have quite as wide usage as oats in skin care, but anecdotal accounts of clove oil use support its efficacy for some people in clearing up acne. But clove oil often causes a numbing or burning sensation that makes it problematic for widespread use in therapeutic quantities. If the acne-fighting ingredient in clove is manganese, though, perhaps we can just put a little manganese in our acne creams and face lotion. Why fill the body with manganese when we just want a little extra affecting our facial pores? (But don't inhale manganese. That's known to lead to neurological damage.)
Manganese seems a beneficial component of cosmetic creams for other reasons. For instance, it helps protect skin from UVA and hydrogen peroxide damage. A manganese enzyme appears to be involved in helping protect connective tissue from age associated abnormalities. And a manganese peptide complex showed promising results in improving the appearance (especially hyperpigmentation) of photodamaged skin, per a 2007 article.
Chronic exposure to excessive manganese leads to manganism, which resembles Parkinson's disease. One of the ways manganism is treated is with chelation using EDTA to lower blood manganese levels. Check every chemical product you own that touches your face, and it probably has EDTA in it as a stabilizer unless you purposely avoid EDTA. If we want some manganese in our skin, I wonder whether we are unwise to use a known chelator of manganese in so many hair and skin care products.