SKIN BARRIER & MOISTURE

Horsetail

Equisetum arvense

also known as shavegrass

Weak — and a real safety concern with long-term use

A primitive plant whose ancestors towered over the dinosaurs, now a knee-high relic with the highest silica content of any common herb. Used traditionally for nails, hair, bones, and as a mild diuretic — but contains an enzyme that depletes vitamin B1, making it unsuitable for daily long-term use.

Rich source of plant silica, which the body uses in connective tissue, hair, and nails
Mild diuretic action
Traditional use for urinary tract support
Topical use for minor wounds and skin healing
Long traditional use as a tonic for connective tissue

Contains thiaminase, an enzyme that breaks down vitamin B1 (thiamine) — long-term internal use can cause B1 deficiency

Look for thiaminase-free preparations (the enzyme is destroyed by heat, so well-prepared tinctures and decoctions are safer than fresh or dried plant)

Limit continuous internal use to a few weeks

Use caution with diuretics — additive water-loss effect

Use caution with diabetes medication — may affect blood sugar

Can deplete potassium with prolonged use

Avoid with heart or kidney conditions

Avoid during pregnancy and nursing

Avoid with chronic alcohol use — already at risk for B1 deficiency

Memorial Sloan Kettering About Herbs · EMA Herbal Medicinal Product Monographs · American Botanical Council HerbMedPro

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