Are there any contraindications to using arnica macerate?

Topically appliedarnica is generally well-tolerated and suitable for all skin types. During patch tests in vivo on the skin of rabbits, mice, and rats, and in clinical trials, arnica extract has proven to be non-irritating, non-sensitising, and non-phototoxic at various concentrations and over short-term use. However, clinical trials have reported allergic contact dermatitis in some subjects, a delayed type IV hypersensitivity reaction, caused by sesquiterpene lactones. Redness, itching, dry skin... if any of these side effects occur when using arnica topically, immediately stop using the product and consult a doctor.

• Case No.1 : In a clinical study involving 443 patients, five subjects (1.1%) showed positive reactions to patch tests with arnica. They were referred for eczematous allergic reactions of the hands or face, resulting in itching and dry skin.

• Case No. 2 : In a study by SUTER A. & al, six allergic reactions out of 79 subjects (7.6%) occurred after a topical application of an arnica gel, twice a day for three to six weeks, for the treatment of mild to moderate knee osteoarthritis. These were primarily mild to moderate local reactions at the site of application, namely an allergy accompanied by redness, itching, skin dryness, an episode of pruritus, an increase in pain, and a localised skin rash.

• Case No. 3 : MELZER J. & al. reported in their double-blind randomised study that adverse effects (itching, irritation, redness) occurred in 5 out of 105 patients (4.8%) receiving topical arnica gel for the treatment of hand osteoarthritis, after 21 days of application.

Further trials involving larger patient cohorts are necessary to assess the safety of using arnica on the skin and the appropriate dosages.

Although it is of natural origin, like any active ingredient applied to the skin, there is always a risk that the skin may react to arnica and develop erythema. Furthermore, being part of the sunflower family and related plants (Asteraceae), individuals allergic to flowering plants of this family should ensure to discuss this with a health professional before considering applying any arnica-based skincare on the skin.

Pregnant women and young children: can they use arnica safely?

It is generally suggested that topical products containing arnica can be safely used during pregnancy and breastfeeding. However, there is limited data available regarding the safety of using arnica topically in children, pregnant women, and breastfeeding mothers. One study documented a case of haemolytic anaemia and an increase in bilirubin in a nine-day-old breastfed infant, which developed 48 hours after the mother consumed a tea made from arnica flowers. Although this was a case following oral ingestion of botanical products containing arnica, particular caution is still required for these groups and it is advised to seek the opinion of your doctor.

When taken orally, arnica can cause serious side effects (dizziness, tremors, gastroenteritis, dry mouth, tachycardia, vomiting, diarrhoea, lethargy and death). It can also cause irritations to the mucous membranes and induce vomiting. It is safe and well tolerated only at very low concentrations, such as those used in homeopathic medicines. Therefore, any internal use should be closely monitored by a medical professional.