The New York company, which calls itself "a direct-to-consumer personal care brand dedicated to reducing single-use plastic waste in the products we use every day," offers subscription refills so customers don't have to buy new bottles.
By Humankind's co-founders Brian Bushell and Joshua Goodman want to make cutting down the amount of disposable plastic in people's daily routine easy and attractive.
They started the brand after Bushell visited Thailand and was horrified by the ocean plastic pollution he saw there.
"Anyone who subscribes to our first three products, deodorant, shampoo, and mouthwash, will eliminate 2.2 kilograms of single-use plastic waste from entering the environment, over a 12-month period," claimed Goodman, who previously worked as an online fundraiser for Barack Obama's 2008 and 2012 presidential campaigns.
The deodorant and mouthwash come in refillable containers that have a lifetime guarantee, but can be recycled if required.
Refills, dubbed "kindfills" by the brand, come in paper pods made of biodegradable paper and shipped in envelopes made from recycled materials.
In order to make the deodorant less wasteful, it arrives in a solid stick that slots into the refillable container.
The shampoo and mouthwash have been specially formulated to be as concentrated as possible, rather than pre-mixed with water, to reduce the packaging needed to deliver and store them.
The mouthwash comes as tablets that can be stored in a permanent container then dissolved in a glass of water as needed.
The shampoo is delivered in the form of a solid bar that can be wetted in the shower or bath and used to wash hair.
"Each By Humankind shampoo bar takes over five weeks to make using a cold-pressed process," said Goodman.
"Our shampoo bars last longer than other bars of the same size," he added. "This is both due to their high density and because our formulas have a high proportion of natural active ingredients."
By Humankind designed the products to be as attractive and convenient as possible in order to encourage people to adopt a more environmentally friendly lifestyle.
"By introducing the concept of refillable containers in personal care, we are asking our customers to keep a permanent object in their bathrooms or homes," Goodman said.
"The challenge is to make a container that people will want to refill, which raises the bar on our design."
The minimalist packages come in a range of gender-neutral colours that were selected to compliment neutral bathroom decor.
The deodorant comes in neon, off-white, grey and charcoal containers, and is available in unscented or eucalyptus versions.
For mouthwash, there is a choice of green or charcoal for the tub, and a choice of mint, spearmint or fruit flavours. The shampoo bars are lemon and lavender scented.
All the products are cruelty-free, and the mouthwash and shampoo are vegan. The deodorant contains beeswax, so isn't vegan.
Once customers have purchased the refillable container, of which $1 (78p) goes towards removing plastic from the ocean, they can choose how often they would like to have refills sent to them.
"We believe there is more to design than just making products attractive, it has to be effective with a great experience to see results in a behavioural shift towards sustainability in personal care," explained Goodman.
"If we can create thoughtful personal care products that are easy to use and are great for the planet, more of us will join in and our impact will reflect that."
Cutting down on disposable plastic bottles is one of the ways that designers can make their products more sustainable.
New York studio Visibility designed a re-fillable container for plant-based deodorant brand Myro, and water brand Evian are trialing a collapsable bubble-style water dispenser with capacity for up to five of its regular bottles.