Sesquiterpene Lactones

What they are. Sesquiterpene lactones (SLs) are a large group of reactive plant compounds, with more than 5,000 known. They are most abundant in the Compositae/Asteraceae (daisy) family (Paulsen 2017) and are the most important allergens in Compositae Allergy. Chamomile’s nobilin and desacetylmatricarin are SLs (DermNet), and parthenolide comes from Feverfew. The same family supplies several popular “natural” eczema remedies: Chamomile, Calendula and Arnica, as well as dandelion, yarrow and tansy. A cream or balm sold as soothing can therefore expose eczematous skin to a known contact allergen. Sesquiterpene Lactones [causes] Compositae Allergy Chamomile [part-of] Sesquiterpene Lactones Calendula [relates] Sesquiterpene Lactones

Why atopic toddlers are at higher risk. In children, screening with the SL mix found 0.5% and 1.8% positive in two studies, and Compositae mixes found 4.2% and 2.6%. All published paediatric case reports involved atopic children, and sensitisation was significantly more common in children with Atopic Dermatitis than in non-atopic children (Paulsen 2008). Of 388 Danish children and adolescents who were patch tested, 3% were Compositae-sensitised, and 11 of the 12 had a personal history of atopy (Paulsen & Andersen 2020). An Italian multicentre review lists the SL mix and Compositae mix among the most frequently reported contact allergens in AD (Bonamonte). In a DermNet-cited trial of massage for children with severe eczema, several children got worse because they had become allergic to the essential oils used, including chamomile. Dandelion and other Compositae weeds seem to be important sensitisers in children. Atopic Dermatitis [relates] Sesquiterpene Lactones Sesquiterpene Lactones [worsens] Atopic Dermatitis Essential Oils [relates] Sesquiterpene Lactones

Testing and practical advice. Patch Testing uses an SL mix plus parthenolide, but plant extracts are often needed too, because the mixes miss some calendula and arnica allergies (DermNet; Paulsen 2008). Compositae allergy should be suspected in an atopic toddler whose eczema flares in summer or after plant contact or garden play, or whose eczema worsens after a herbal cream. Swallowed SLs, for example in chamomile tea, can rarely cause systemic allergic dermatitis in people who are already sensitised. The evidence for this is mostly anecdotal, but some oral challenges have confirmed it (Paulsen 2017). For a child with eczema, the lower-risk choice is a plain, botanical-free emollient. Patch Testing [defines] Compositae Allergy Allergic Contact Dermatitis [relates] Sesquiterpene Lactones

Connections

• Compositae Allergy — main allergen class, source: DermNet
• Chamomile — nobilin/desacetylmatricarin are SLs, source: DermNet
• Calendula — Compositae SL-containing remedy, source: Reider 2001
• Arnica — arnica extract added to patch tests for Compositae allergy, source: DermNet
• Feverfew — source of parthenolide, tested alongside SL mix, source: DermNet
• Patch Testing — SL mix + parthenolide, supplement with plant extracts, source: Paulsen 2008
• Atopic Dermatitis — Compositae sensitisation higher in atopic children, source: Paulsen 2008; Paulsen & Andersen 2020
• Allergic Contact Dermatitis — SL mix among most frequent allergens in AD, source: Bonamonte (Contact Dermatitis)