Citral

What is citral?

Citral (INCI: Citral) is a lemon-scented monoterpene aldehyde — actually a blend of two isomers, geranial and neral — responsible for that bright, clean citrus smell. It's abundant in nature: lemongrass oil is roughly 70–80% citral, and it's also found in lemon (~6%), lime, citronella, and lemon balm oils. It's used both as an isolated fragrance chemical and, very often, as a natural component of citrus and lemongrass oils added to formulas.

It's one of the six components of Fragrance Mix II (FM II), the patch-test screen for fragrance allergies that the older Fragrance Mix I can miss, and an EU-labelled allergen.

Why it causes reactions — and the "natural" paradox

Citral is an α,β-unsaturated aldehyde, a reactive structure that readily binds skin proteins to form the haptens behind Type IV contact allergy. Like its terpene cousins linalool and limonene, citral also oxidises on air exposure into more allergenic products, so older products carry more risk.

The most important practical point is the "natural" paradox: citral in lemongrass or citrus oil is identical to synthetic citral, and lemongrass oil is mostly citral. So the rise of "clean," essential-oil-forward skincare has actually increased citral exposure for the very shoppers trying to avoid "chemicals." Natural origin offers no protection here.

A note on sunlight: citral itself has only weak phototoxic potential. The dramatic sun-triggered reactions associated with citrus oils are usually due to furocoumarins (such as bergapten in bergamot) — separate phototoxic compounds — not citral. The citral issue is primarily contact allergy.

How to spot and avoid it

1. Read labels for Citral (also Geranial, Neral, Lemonal) and for Cymbopogon (Lemongrass) Oil, Citrus Limon (Lemon) Peel Oil, and lime/citronella oils.
2. Be especially careful with "natural"/aromatherapy products — lemongrass is the highest-citral source.
3. Avoid related citrus/rose terpenes (limonene, geraniol) if you cross-react.
4. Don't apply undiluted citrus essential oils before sun (a furocoumarin caution, separate from citral allergy).

Safer alternatives

• Fragrance-free personal care to remove citral entirely.
• Non-citrus household cleaners (lavender — but check for linalool allergy — or unscented).
• If using essential oils, work with someone knowledgeable about allergens; rose, chamomile, and calendula are lower in citral.

The bottom line

Citral is the lemongrass-and-citrus lemon note, a Fragrance Mix II allergen that oxidises readily — and the clearest example of why "natural" essential oils are not low-allergen. If you react, treat lemongrass and citrus oils as the same allergen as synthetic citral, and watch its terpene relatives too.