Teens First Period: A Parent's Guide to Period Underwear

Quick answer

For a teen's first period, start with two to three pairs of comfortable, age-appropriate period underwear like the Teen Period Ready Pack - Black or Teens Side Seamfree Bikini Brief. Look for absorbency around 15–20ml (roughly 3–4 regular tampons), a seamless or soft waistband, and a fit that stays put without digging in. If swimming is a concern, add a pair of period swim bottoms such as the Teen First Swim Bikini Crop - Black.

Your teen's first period can feel like a lot to manage—for both of you. Between school, sport, sleepovers, and everything else, the last thing they need is to worry about leaks. Period underwear is a practical, reusable option that works like regular underwear but absorbs flow, making it a gentle introduction to menstrual care.

This guide walks you through what actually matters when choosing first period underwear for teens: absorbency, fit, style, and how to build a small starter set. You'll also find specific product examples from Love Luna that are designed for younger, growing bodies.

Why period underwear makes sense for a first period

Period underwear is worn like normal underwear and has built-in layers that absorb blood and keep it locked away. For a teenager, that means no fiddling with pads that shift or tampons that can feel intimidating. It's also reusable—just rinse and wash—so it's a more sustainable and often more economical choice over time.

Many teens feel more confident wearing something that looks and feels like their everyday underwear. Love Luna's teen range is specifically designed for tweens and teens in junior sizes, with softer fabrics and a fit that accommodates growing bodies.

• Period underwear can be worn alone on lighter days or as back-up with a pad or tampon on heavier days.
• It's ideal for school, sport, and overnight because it stays in place and doesn't need changing during the day.

Key features to look for in teen period underwear

Absorbency is measured in millilitres (ml). For a first period, a capacity of 15–20ml (about 3–4 regular tampons) is a good starting point. That's enough for light to moderate flow and gives your teen a safety net while they learn their cycle. Love Luna's Teen Side Seamfree Bikini Brief, for example, absorbs 15–20ml.

Fit matters as much as absorbency. Seamfree or seamless styles reduce rubbing under tight clothing, and an elastic binding at the leg openings helps stop the briefs from riding up. A high-waisted full brief can feel more secure over the tummy, while a bikini shape is a familiar, comfortable cut for most teens.

• Check the absorbency rating: 15–20ml is a good starting point for beginners.
• Look for soft, stretchy fabrics and seamless construction for comfort.
• Ensure the leg openings have a gentle elastic to prevent riding up.

How to choose the right style for your teen

The best style is the one your teen will actually wear. Bikini briefs are a classic choice and work well under most outfits. Full briefs offer more coverage and can feel more secure for overnight or heavy flow days. For swimming, period swimwear is a game-changer—it looks like regular swimwear but has absorbent layers and a water-repellent finish.

If your teen is active, consider a seamless bikini brief for sport and a full brief for sleep. Having a mix means they're covered for different activities and flow levels. A discreet carry bag, like the one in the Teen Period Ready Pack, makes it easy to carry a spare pair to school without anyone knowing.

• Bikini brief: everyday comfort, great for lighter days and school.
• Full brief: extra coverage, ideal for overnight or heavier days.
• Period swimwear: for pool days and beach trips without worry.

Building a starter set: how many pairs?

A period usually lasts 3–7 days, and flow varies. For a first period, start with 3–5 pairs so your teen has enough to change as needed without doing laundry every day. A pack like the Teen Period Ready Pack - Black includes two pairs of First Period Briefs plus a silicone leakproof bag, which is a practical way to begin.

If your teen has a heavier flow, add one or two full briefs for overnight. If they swim regularly, one pair of period swim bottoms is worth it. You can always expand the collection as you learn what works best.

• Start with 3–5 pairs for a full cycle.
• Include at least one full brief for heavier days or sleep.
• Add period swimwear if swimming is part of their routine.

Fit guidance: getting the size right

Period underwear should fit snugly but not tightly. It needs to sit close to the body to prevent leaks, but it shouldn't leave deep marks or feel restrictive. Love Luna's teen range is made in junior sizes for younger, growing bodies, so check the size chart carefully. If your teen is between sizes, size up for comfort—the absorbent layers will still do their job.

For a seamless bikini brief, the waistband should lie flat against the skin without rolling down. The leg openings should have a gentle elastic that stays in place but doesn't dig in. If your teen is taller or has a longer torso, a full brief may provide a more secure fit. Always wash new period underwear before first wear according to the care instructions.

• Measure your teen's waist and hips, then compare to the size chart.
• Size up if between sizes—comfort is key for first-time users.
• Check that the leg elastic sits flat and doesn't ride up when moving.

Decision rules for choosing teen period underwear

• If your teen is new to periods and wants a simple start: Choose a bikini brief with 15–20ml absorbency, like the Teens Side Seamfree Bikini Brief. It's easy to wear and feels like regular underwear. Start with 3–5 pairs to cover a full cycle.
• If your teen has a heavier flow or needs overnight security: Add a full brief style for extra coverage. The Side Seamfree Period Full Brief has a high-waisted design and full bum coverage. Use full briefs for sleep and heavy days, bikinis for lighter days.
• If your teen swims or has PE at school: Choose period swimwear like the Teen First Swim Bikini Crop paired with period swim bottoms. They look like normal swimwear and have water-repellent protection. One pair of period swim bottoms is enough to start.
• If your teen is between sizes: Size up for comfort. The absorbent layers work regardless of slight looseness, and a snug-but-not-tight fit prevents leaks. Check the size chart and prioritize comfort over a perfect match.

Love Luna products for a teen's first period

• Teen Period Ready Pack - Black: Includes two pairs of Love Luna First Period Briefs in a classic bikini shape, plus a silicone leakproof bag for discreet storage. A complete starter kit that makes it easy to carry spare briefs to school or activities without embarrassment.
• Teens Side Seamfree Bikini Brief: Absorbs 15–20ml (3–4 regular tampons) and features seamless knitting technology with elastic binding at leg openings to stop riding up. Provides reliable absorbency for light to moderate flow with a smooth, comfortable fit under clothes—ideal for everyday wear.
• Teen First Swim Bikini Crop - Black: Designed to match back with Love Luna period swim bottoms; fully lined with water-repellent treatment and a built-in bra. Lets teens swim confidently during their period when paired with period swim bottoms, so they don't miss out on pool days.
• Adult Period Swim Full Brief - Black: Features 4 layers of protection and water-repellent fabric to keep periods locked away in and out of the water. A good option for older teens or those who prefer a full brief cut for swimming, offering the same trusted protection.

Fit guidance for teen period underwear

Best for

• Teens who want underwear that feels like their regular bikini briefs
• Active teens who need leak protection for school and sport
• Overnight use when paired with a full brief style

Not for

• Those looking for a disposable option—period underwear is reusable and requires washing
• Teens who prefer tampons or pads exclusively; period underwear can be used as back-up but is not a replacement for medical advice

Choosing the first period underwear for your teen doesn't have to be overwhelming. Focus on absorbency, fit, and styles that match their daily life. With a few well-chosen pairs from Love Luna's teen range, your teen can feel prepared and confident—whether they're at school, playing sport, or swimming.