The science
The stick's protection rests on three organic filters. Avobenzone at 3 percent is the only UVA filter and absorbs across UVA1, which is what earns the broad-spectrum and PA+++ designations; it is photolabile, degrading under UV unless stabilised, and in the absence of octocrylene or bemotrizinol this formula relies on butyloctyl salicylate, the ester base and the antioxidant tail to slow that degradation, an approach that works but gives less margin than an octocrylene-stabilised system, which argues for the two-hour reapplication the brand recommends. Homosalate and octisalate at 5 percent each are UVB salicylate filters with modest individual SPF contributions that combine with avobenzone to reach the labelled SPF 45; both are photostable, both are common eye irritants in sticks that migrate, and homosalate is under FDA data-request review with the other older organic filters, with a proposed European maximum of 7.3 percent. The PA+++ rating corresponds to a persistent-pigment-darkening ratio of 8 to under 16 under ISO 24442, a genuine in-vivo UVA measure not required for US sale.
The balm base determines the finish and the dosing problem. Neopentyl glycol dicaprylate/dicaprate, octyldodecanol, a C15-19 alkane, coco-caprylate and squalane are light emollient esters and hydrocarbons that dissolve the filters and glide; dibutyl lauroyl glutamide and dibutyl ethylhexanoyl glutamide are low-molecular-weight gelling agents that structure the oil phase into a clear stick without wax; silica silylate thickens and reduces greasiness; polyester-8 and a VP/eicosene copolymer form a water-resistant film. Sunscreen SPF is determined at an application density of 2 milligrams per square centimetre, and published studies of stick application find typical user deposition well below that, so the effective protection depends heavily on the brand's four-passes instruction being followed. Watermelon and meadowfoam seed oils add fatty acids; tocopheryl acetate, pentaerythrityl tetra-di-t-butyl hydroxyhydrocinnamate and tetrahexyldecyl ascorbate form an antioxidant system that quenches UV-generated radicals and has supporting evidence for reducing UV damage markers beneath a sunscreen. Sodium hyaluronate, niacinamide and Crithmum maritimum extract close the list at trace concentrations; niacinamide's documented effects on pigment transfer and barrier lipids occur at 2 to 5 percent and cannot be attributed to this product.
Tolerability follows the chemistry: organic salicylate filters and fragrance in a low-melt base migrating to the eyes cause stinging in a subset of users; the parfum adds a contact-allergy risk; avobenzone is an occasional photocontact allergen. The formula is free of silicones, water, alcohol and mineral filters. On pregnancy, US organic filters are considered acceptable by most guidance though mineral filters are often preferred; individual advice applies.