Biotin has a genuine, authorised place in this category: it contributes to the maintenance of normal hair and normal skin. The important word is "maintenance" — biotin supports the hair and skin you already have functioning normally, rather than being a proven treatment for hair loss or thinning. Most people get enough biotin from a varied diet, so supplementing tends to matter most if your intake is genuinely low rather than as a universal fix. If nail health specifically is your goal, zinc and selenium carry the more directly relevant authorised claims (normal nails), so a combination formula covering all three is often a more complete approach than biotin alone. Worth noting: high-dose biotin supplements can interfere with certain thyroid blood test results, so it's worth mentioning to your GP or a lab technician if you're taking one and having blood tests done.

Here's the straightforward version: collagen supplements do not currently carry an authorised claim for skin appearance under GB or EU rules — despite how widely they're marketed that way. What is authorised is Vitamin C's contribution to normal collagen formation, which supports the collagen your body already produces. If skin appearance specifically is your goal, a collagen product with added Vitamin C is a reasonable combination, but it's worth buying it for the ingredients you're comfortable with rather than an implied outcome. We keep a dedicated Collagen collection separately, covering marine and bovine sources, powders and capsules, if that's specifically what you're comparing.

• Single-nutrient products (zinc-only, biotin-only, selenium-only) suit anyone who's identified a specific gap or wants precise control over dosage.
• Combination formulas bundle several of these nutrients together — useful if you want broad daily coverage without buying four separate products, though check the individual doses aren't diluted below a meaningful level.

If you're unsure where to start, a combination formula covering biotin, zinc and selenium touches all three authorised claim areas (hair, skin, nails) in one product, which is a sensible default before narrowing down to single-nutrient supplementing later.

If brittle or splitting nails is the main concern, zinc and selenium are your closest authorised-claim matches. If it's hair specifically, biotin and zinc both carry direct authorised claims for normal hair. If it's skin texture or tone, biotin and Vitamin C (via its collagen-formation claim) are the relevant options — skin appearance beyond that is outside what any supplement here is authorised to claim. In all cases, these products work as nutritional support alongside a balanced diet, not as a substitute for addressing an underlying cause — if a concern is sudden, severe, or persistent, it's worth a conversation with a GP rather than supplementing alone.

We won't pretend this range isn't affected — a significant portion of products here are currently sold out while we restock, including some of our most popular combination formulas. We've deliberately kept the full range visible rather than hiding sold-out items, so you can see the complete picture rather than assuming discontinuation. If your preferred product is unavailable, the most efficient approach is usually to compare which authorised nutrients it contained (biotin, zinc, selenium, Vitamin C) and choose an in-stock alternative covering the same ones, rather than waiting on a specific brand — most products in this space are more similar in substance than their packaging suggests.