Sun exposure can accelerate ageing, cause skin burns, erythema (a skin reaction), skin cancer, melasmas (or sun spots) and other forms of hyperpigmentation – all triggered by solar ultraviolet radiation.

Approximately 80% of skin cancer cases in people engaged in outdoor activities are preventable by decreasing sun exposure. This can be done in lots of ways including wearing protective clothing or sunscreens.

But not all sunscreens work in the same way. You might have heard of “physical” and “chemical” sunscreens. What’s the difference and which one is right for you?

How sunscreens are classified

Sunscreens are grouped by their use of active inorganic and organic ultraviolet (UV) filters. Chemical sunscreens use organic filters such as cinnamates (chemically related to cinnamon oil) and benzophenones. Physical sunscreens (sometimes called mineral sunscreens) use inorganic filters such as titanium and zinc oxide.

These filters prevent the effects of UV radiation on the skin.

Organic UV filters are known as chemical filters because the molecules in them change to stop UV radiation reaching the skin. Inorganic UV filters are known as physical filters, because they work through physical means, such as blocking, scattering and reflection of UV radiation to prevent skin damage.

Nano versus micro

The effectiveness of the filters in physical sunscreen depends on factors including the size of the particle, how it’s mixed into the cream or lotion, the amount used and the refraction index (the speed light travels through a substance) of each filter.

When the particle size in physical sunscreens is large, it causes the light to be scattered and reflected more. That means physical sunscreens can be more obvious on the skin, which can reduce their cosmetic appeal.

Nanoparticulate forms of physical sunscreens (with tiny particles smaller than 100 nanometers) can improve the cosmetic appearance of creams on the skin and UV protection, because the particles in this size range absorb more radiation than they reflect. These are sometimes labelled as “invisible” zinc or mineral formulations and are considered safe.

So how do chemical sunscreens work?

Chemical UV filters work by absorbing high-energy UV rays. This leads to the filter molecules interacting with sunlight and changing chemically.

When molecules return to their ground (or lower energy) state, they release energy as heat, distributed all over the skin. This may lead to uncomfortable reactions for people with skin sensitivity.

Generally, UV filters are meant to stay on the epidermis (the first skin layer) surface to protect it from UV radiation. When they enter into the dermis (the connective tissue layer) and bloodstream, this can lead to skin sensitivity and increase the risk of toxicity. The safety profile of chemical UV filters may depend on whether their small molecular size allows them to penetrate the skin.

Chemical sunscreens, compared to physical ones, cause more adverse reactions in the skin because of chemical changes in their molecules. In addition, some chemical filters, such as dibenzoylmethane tend to break down after UV exposure. These degraded products can no longer protect the skin against UV and, if they penetrate the skin, can cause cell damage.

Due to their stability – that is, how well they retain product integrity and effectiveness when exposed to sunlight – physical sunscreens may be more suitable for children and people with skin allergies.

Although sunscreen filter ingredients can rarely cause true allergic dermatitis, patients with photodermatoses (where the skin reacts to light) and eczema have higher risk and should take care and seek advice.

What to look for

The best way to check if you’ll have a reaction to a physical or chemical sunscreen is to patch test it on a small area of skin.

And the best sunscreen to choose is one that provides broad-spectrum protection, is water and sweat-resistant, has a high sun protection factor (SPF), is easy to apply and has a low allergy risk.

Health authorities recommend sunscreen to prevent sun damage and cancer. Chemical sunscreens have the potential to penetrate the skin and may cause irritation for some people. Physical sunscreens are considered safe and effective and nanoparticulate formulations can increase their appeal and ease of use.

Yousuf Mohammed, Dermatology researcher, The University of Queensland and Khanh Phan, Postdoctoral research associate, Frazer Institute, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Readers are advised this article includes an offensive and outdated disability term in a quote from the film.

Poor Things is a spectacular film that has garnered critical praise, scooped up awards and has 11 Oscar nominations. That might be the problem. Audiences become absorbed in another world, so much so our usual frames of reference disappear.

There has been much discussion about the film’s feminist potential (or betrayal). What’s not being talked about in mainstream reviews is disability. This seems strange when two of the film’s main characters are disabled.

Set in a fantasy version of Victorian London, unorthodox Dr Godwin Baxter (William Dafoe) finds the just-dead body of a heavily pregnant woman in the Thames River. In keeping with his menagerie of hybrid animals, Godwin removes the unborn baby’s brain and puts it into the skull of its mother, who becomes Bella Baxter (Emma Stone).

Is Bella really disabled?

Stone has been praised for her ability to embody a small child who rapidly matures into a hypersexual person – one who has not had time to absorb the restrictive rules of gender or patriarchy.

But we also see a woman using her behaviour to express herself because she has complex communication barriers. We see a woman who is highly sensitive and responsive to the sensory world around her. A woman moving through and seeing the world differently – just like the fish-eye lens used in many scenes.

Women like this exist and they have historically been confined, studied and monitored like Bella. When medical student Max McCandless (Ramy Youssef) first meets Bella, he offensively exclaims “what a very pretty retard!” before being told the truth and promptly declared her future husband.

Even if Bella is not coded as disabled through her movements, speech and behaviour, her onscreen creator and guardian is. Godwin Baxter has facial differences and other impairments which require assistive technology.

So ignoring disability as a theme of the film seems determined and overt. The absurd humour for which the film is being lauded is often at Bella’s “primitive”, “monstrous” or “damaged” actions: words which aren’t usually used to describe children, but have been used to describe disabled people throughout history.

In reviews, Bella’s walk and speech are compared to characters like the Scarecrow in The Wizard of Oz, rather than a disabled woman. So why the resistance?

Freak shows and displays

Disability studies scholar Rosemarie Gardland-Thomson writes “the history of disabled people in the Western world is in part the history of being on display”.

In the 19th century, when Poor Things is set, “freak shows” featuring disabled people, Indigenous people and others with bodily differences were extremely popular.

Doctors used freak shows to find specimens – like Joseph Merrick (also known as the Elephant Man and later depicted on screen) who was used for entertainment before he was exhibited in lecture halls. In the mid-1800s, as medicine became a profession, observing the disabled body shifted from a public spectacle to a private medical gaze that labelled disability as “sick” and pathologised it.

Poor Things doesn’t just circle around these discourses of disability. Bella’s body is a medical experiment, kept locked away for the private viewing of male doctors who take notes about her every move in small pads. While there is something glorious, intimate and familiar about Bella’s discovery of her own sexual pleasure, she immediately recognises it as worth recording in the third person:

I’ve discovered something that I must share […] Bella discover happy when she want!

The film’s narrative arc ends with Bella herself training to be a doctor but one whose more visible disabilities have disappeared.

Framing charity and sexual abuse

Even the film’s title is an expression often used to describe disabled people. The charity model of disability sees disabled people as needing pity and support from others. Financial poverty is briefly shown at a far-off port in the film and Bella initially becomes a sex worker in Paris for money – but her more pressing concern is sexual pleasure.

Disabled women’s sexuality is usually seen as something that needs to be controlled. It is frequently assumed disabled women are either hypersexual or de-gendered and sexually innocent.

In the real world disabled people experience much higher rates of abuse, including sexual assault, than others. Last year’s Royal Commission into Violence, Abuse, Neglect and Exploitation of People with Disability found women with disability are nearly twice as likely as women without disability to have been assaulted. Almost a third of women with disability have experienced sexual assault by the age of 15. Bella’s hypersexual curiosity appears to give her some layer of protection – but that portrayal denies the lived experience of many.

Watch but don’t ignore

Poor Things is a stunning film. But ignoring disability in the production ignores the ways in which the representation of disabled bodies play into deep and historical stereotypes about disabled people.

These representations continue to shape lives.

Louisa Smith, Senior lecturer, Deakin University; Gemma Digby, Lecturer – Health & Social Development, Deakin University, and Shane Clifton, Associate Professor of Practice, School of Health Sciences and the Centre for Disability Research and Policy, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.