SPF vs PA Explained: Why You Still Tan Despite Wearing Sunscreen

Understanding SPF vs PA is essential for choosing effective sun protection. SPF measures protection against UVB rays that mainly cause sunburn and surface-level skin damage, while PA measures protection against UVA rays linked to tanning, pigmentation, melasma, collagen breakdown, and premature ageing.

If you wear sunscreen daily but still experience tanning, pigmentation, or uneven skin tone, your sunscreen may not be protecting against the right type of UV damage. Many people focus only on high SPF numbers while completely ignoring UVA protection, which is one of the biggest reasons tanning and pigmentation still occur despite regular sunscreen use.

A broad-spectrum sunscreen with balanced SPF and PA protection is far more effective than simply choosing the highest SPF available. For Indian skin types and humid climates, where tanning, post-inflammatory pigmentation, and sun-induced skin damage are especially common, understanding both SPF and PA can help you choose a sunscreen better suited to your skin type, lifestyle, and daily sun exposure.

UVA vs UVB Rays: What’s the Difference? 

The sun emits two major types of ultraviolet (UV) rays that damage the skin: UVA and UVB.

UVA and UVB rays affect the skin in different ways, which is why effective sun protection should defend against both types of UV exposure.

UVB rays mainly cause sunburn, while UVA rays penetrate deeper and contribute to tanning, pigmentation, and premature skin ageing.

UVB Rays

UVB rays mainly affect the outer layers of the skin and are primarily responsible for:

• Sunburn

• Redness and irritation

• Direct DNA damage linked to skin cancer risk

UVA Rays

UVA rays penetrate deeper into the skin and contribute to:

• Tanning

• Hyperpigmentation and melasma

• Collagen breakdown

• Fine lines and premature ageing

• Long-term photoaging

This is where SPF and PA ratings become important:

• SPF measures protection against UVB rays.

• PA measures protection against UVA rays

Many people focus heavily on high SPF numbers while barely checking UVA protection. This is one of the biggest reasons people continue experiencing tanning, pigmentation, and uneven skin tone despite using sunscreen regularly.

Research published by the National Center for Biotechnology Information shows that chronic UVA exposure plays a significant role in photoaging, pigmentation disorders, and visible skin ageing, especially in skin of colour.

What Does SPF Mean in Sunscreen?

SPF (Sun Protection Factor) measures how effectively a sunscreen protects the skin against UVB rays, which are primarily responsible for sunburn and surface-level skin damage.

One of the biggest misconceptions around sunscreen is that extremely high SPF numbers provide dramatically stronger protection. In reality, the increase in UVB protection becomes smaller as SPF numbers rise.

Here’s a simplified comparison:

This means the jump from SPF 50 to SPF 100 is far less dramatic than most sunscreen marketing makes it appear.

More importantly, higher SPF does not eliminate the need for proper application and regular reapplication. Sunscreen protection gradually decreases with sweating, swimming, friction, humidity, and prolonged sun exposure.

The American Academy of Dermatology recommends reapplying sunscreen every two hours during outdoor exposure, especially after sweating or swimming.

How Is SPF Calculated?

Many people search for how SPF is calculated, but SPF is not something consumers calculate manually at home. Sunscreen SPF testing is performed under controlled laboratory conditions using standardised application amounts and UV exposure measurements.

In simple terms, SPF estimates how much longer sunscreen can help protect the skin from UVB-induced sunburn compared to unprotected skin.

For example:

• If unprotected skin starts burning in 10 minutes

• And sunscreen delays burning for approximately 300 minutes

The sunscreen theoretically provides SPF 30 protection under laboratory conditions.

However, real-world sunscreen protection often looks very different outside the lab.

Factors such as:

• Sweat and humidity

• Under-application

• Swimming and friction

• Pollution and oil buildup

• Delayed reapplication

can significantly reduce the level of protection sunscreen actually delivers throughout the day.

This is especially important because most people apply far less sunscreen than the amount used during SPF testing. As a result, an SPF 50 sunscreen may perform much closer to SPF 15 in real-world usage when applied inadequately.

What Does PA Mean in Sunscreen?

PA stands for Protection Grade of UVA and measures how effectively a sunscreen protects the skin against UVA rays. Unlike UVB rays, which mainly cause sunburn, UVA rays penetrate deeper into the skin and contribute to long-term skin damage.

UVA exposure is strongly associated with:

• Tanning

• Hyperpigmentation

• Melasma

• Collagen breakdown

• Fine lines and wrinkles

• Premature skin ageing (photoaging)

One of the biggest reasons many people still experience tanning and pigmentation despite wearing sunscreen daily is inadequate UVA protection. This is why PA ratings are especially important for pigmentation-prone skin types.

Unlike sunburn caused by UVB rays, UVA damage develops gradually and may not always be immediately visible. However, repeated UVA exposure can contribute to uneven skin tone, persistent pigmentation, and accelerated signs of ageing over time.

This becomes even more important in countries like India, where intense UV exposure, heat, humidity, and post-inflammatory pigmentation are common skin concerns throughout the year.

What Is PA Rating in Sunscreen?

PA ratings indicate how effectively a sunscreen protects the skin against UVA rays linked to tanning, pigmentation, melasma, and photoaging.

The PA system is generally classified as:

These ratings are based on a testing method called Persistent Pigment Darkening (PPD), which measures how effectively sunscreen protects against UVA-induced pigmentation and skin darkening.

For example:

• A PA+++ sunscreen has a PPD value between 8 and 16.

• A PA++++ sunscreen has a PPD of at least 16, making it one of the best choices for pigmentation-prone skin and intense sun exposure. (JCIA, Sept 1st, 2022)

Unlike SPF testing, which primarily measures protection against UVB-induced sunburn, PA ratings specifically evaluate protection against long-wave UVA rays that penetrate deeper into the skin and contribute to collagen breakdown, uneven skin tone, and premature skin ageing over time.

For daily sunscreen use, especially in hot and humid climates like India, dermatologists generally recommend choosing at least PA+++ broad-spectrum protection. For individuals dealing with melasma, post-inflammatory hyperpigmentation, tanning, or prolonged outdoor exposure, PA++++ protection is often the better option.

SPF vs PA – Which One Matters More?

SPF and PA protect the skin against different types of ultraviolet damage, which means both are important for complete sun protection.

Here’s a simplified comparison:

While SPF protects against surface-level UVB damage, PA ratings evaluate protection against deeper UVA exposure associated with pigmentation, melasma, collagen breakdown, and premature skin ageing.

A 2025 study has shown that a sunscreen with an extremely high SPF but inadequate UVA protection may still allow tanning, uneven skin tone, and long-term photoaging to develop over time. This is why dermatologists increasingly recommend choosing broad-spectrum sunscreen with balanced SPF and PA protection rather than focusing only on very high SPF numbers.

For most people, especially in climates with intense sunlight and high UV exposure, a broad-spectrum sunscreen with SPF 50-100 and PA+++ or PA++++ protection is generally considered sufficient for daily use.

So Which Sunscreen Should You Actually Choose?

For daily sunscreen use, a broad-spectrum sunscreen with SPF 50-100 and PA+++ or PA++++ protection is generally sufficient for most skin types and indoor-to-outdoor daily exposure.

For prolonged outdoor activities, sports, beach exposure, or pigmentation-prone skin, choosing a sunscreen with stronger UVA protection, water resistance, and consistent reapplication becomes even more important.

Texture and wearability also play a major role in how effectively sunscreen performs in real-world conditions. In hot and humid climates like India, heavy or greasy sunscreens often feel uncomfortable during extended wear, which can reduce proper reapplication throughout the day.

Lightweight aqua gel sunscreen formulations are often preferred for humid weather because they feel more breathable on the skin and are easier to reapply consistently. Mist sunscreens can also make reapplication more convenient during travel, outdoor activities, or long workdays.

The Biggest Sunscreen Mistakes Almost Everyone Makes

One of the biggest sunscreen mistakes is not necessarily choosing the “wrong” SPF — it’s applying too little sunscreen to achieve the level of protection stated on the label.

Most people apply significantly less sunscreen than the amount used during SPF testing, which can dramatically reduce real-world protection against both UVB and UVA damage.

Dermatologists generally recommend using approximately two to three finger lengths of sunscreen for the face and neck, along with consistent reapplication every two hours during prolonged outdoor exposure, sweating, or swimming.

Proper application matters just as much as choosing the right SPF or PA rating. If you want a detailed step-by-step guide, you can read our guide on how to apply sunscreen correctly for daily use.

SPF vs PA: What Actually Matters Most?

One of the biggest sunscreen myths is that higher SPF automatically means better overall protection. In reality, effective sun protection depends on balanced broad-spectrum coverage against both UVB and UVA rays.

While SPF mainly measures protection against sunburn-causing UVB rays, PA ratings help evaluate protection against UVA rays linked to tanning, pigmentation, melasma, collagen breakdown, and premature skin ageing.

Focusing only on extremely high SPF numbers while ignoring UVA protection is one of the biggest reasons many people still experience tanning and uneven skin tone despite using sunscreen regularly.

In real-world use, a sunscreen that feels comfortable enough for consistent daily wear and reapplication will usually protect the skin more effectively than an extremely high-SPF formula that feels too heavy, greasy, or uncomfortable to use properly.

For most skin types, the best sunscreen is typically a broad-spectrum formula with SPF 50-100 and PA+++ or PA++++ protection that you can apply generously and reapply consistently every day.