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Alert. patches use a photochromic compound — a molecule that changes colour when exposed to UV light. When your sunscreen is active, it absorbs UV before it reaches the patch, keeping the compound (and the patch) clear. When your sunscreen degrades, UV passes through unchecked and activates the compound, turning the patch purple. It's a direct, real-time measurement of how much UV is reaching your skin.

The patch doesn't measure your SPF factor directly. Instead, it detects whether UV is being blocked from reaching the patch surface. Think of it as a UV pass/fail test for your sunscreen — clear means the SPF is still filtering effectively, purple means it's no longer protecting you adequately. The colour change is a practical indicator, not a lab measurement.

The patch needs time to calibrate with your skin's environment. When first applied, the photochromic compound is establishing a baseline response relative to the UV filtering layer of your sunscreen. During this 30-minute window the patch may appear tinted or unclear — this is completely normal and doesn't mean anything is wrong. After 30 minutes the patch has stabilised and will give you accurate readings for the rest of the day. Do not judge protection level during the calibration period.

Yes. Alert. patches work with all mineral and chemical sunscreens regardless of brand, as long as the SPF factor is 30 or above. The patch responds to the UV-filtering effect of the sunscreen, not any particular ingredient. We recommend SPF 50 in high-UV environments for best results and maximum protection.

Each patch is designed for a single day's use. The photochromic compound resets multiple times throughout the day as you reapply sunscreen — so the purple→clear→purple cycle can happen several times on one patch. However, the adhesive and compound are designed for daily use rather than multi-day reuse. Replace the patch each morning, or sooner if adhesion weakens.

We recommend your wrist, forearm, or shoulder — somewhere you'll naturally glance throughout the day. The key is visibility. A patch you don't notice isn't helping you. Avoid placing it over joints that flex a lot (like the inside of your wrist), and avoid placing it on areas covered by clothing as this will affect the UV reading.

Apply your sunscreen first, then apply the patch to a separate area of clean skin. Do not apply the patch directly on top of sunscreen — the patch should sit on bare skin adjacent to your sunscreened skin. The patch detects the UV-filtering layer through indirect detection of ambient UV reaching the patch surface.

A few things can affect how quickly the patch clears. If you're using a lower SPF factor (30–40), the patch may take slightly longer to fully clear compared to SPF 50. Very high UV intensity can also slow the clearing process. If the patch still appears purple or very tinted after 45 minutes in the shade, reapply your sunscreen — it's better to be cautious. Make sure you've applied a generous, even layer of sunscreen.

Alert. patches are water resistant and will stay adhered through swimming and sweat. However, we always recommend reapplying sunscreen after any water activity regardless of what colour the patch is — water accelerates sunscreen breakdown significantly. After reapplying, wait the 30 minutes again for the patch to recalibrate.

Yes — and this is one of the most important use cases. Up to 80% of UV radiation passes through cloud cover, meaning you can burn on an overcast day. Alert. patches respond to UV regardless of visible sunshine, so they'll still turn purple when your sunscreen breaks down even when it doesn't feel hot or sunny.

Alert. patches use a gentle adhesive designed for comfortable, everyday wear. As with any adhesive product, if you experience any irritation, remove the patch and discontinue use. If irritation persists, consult a healthcare professional.

Alert. patches are safe for use on children's skin and are an excellent tool for making sun safety visible and engaging for kids. We recommend adult supervision for children under 3. Always ensure children do not put patches in their mouth — while the materials are non-toxic, patches are not intended for ingestion.

Alert. patches are designed for external use only and do not transfer any substance into the skin. The photochromic compound is contained within the patch layer and stays there. As always, if you have any concerns during pregnancy, we recommend consulting your healthcare provider before using any new product on your skin.

No. The photochromic compound is sealed within the patch and does not transfer to skin. The only thing that contacts your skin is the adhesive layer. Alert. patches are a detection tool, not a topical treatment — nothing is delivered to your skin through them.

Shipping is always free within Ireland, no minimum order required. For the rest of the EU and worldwide, standard shipping is free on orders over €30; orders under €30 incur a flat shipping fee. We ship from Ireland and typical delivery times are 2–5 business days within Ireland and the EU, and 5–10 days for international orders.

Yes, we ship worldwide. Delivery times and rates vary by destination. All international orders are tracked and you'll receive a tracking number by email once your order has been dispatched.

We aim to dispatch all orders within 1–2 business days. Standard delivery within Ireland and the EU typically takes 2–5 business days after dispatch. Express shipping options are available at checkout if you need your order sooner.

We offer a 30-day satisfaction guarantee. If you're not happy with your Alert. patches for any reason, contact us within 30 days of receiving your order and we'll arrange a full refund. Unopened packs can be returned for a full refund. For opened packs where the product isn't performing as expected, please contact us with details and we'll find a solution.

First, check that you've waited the full 30 minutes after application and that the patch is applied to clean, bare skin (not directly on sunscreen). If you've followed all instructions and the patches still aren't working correctly, please contact us at alertswimwear@gmail.com with a description of what you're experiencing. We'll troubleshoot with you and if the product is faulty, we'll replace it immediately.

Email us at alertswimwear@gmail.com with your order number and reason for return. We'll respond within 24 hours with return instructions. You don't need to send anything back before we process your refund for faulty products — we just need a brief description of the issue.