I have pillow covers on my (non-feather) pillows, I got them a long time ago so I don't remember where. They're woven fabric, no plastic backing on the inside. I would imagine there's lots of this type of thing on the market.

I am sensitive to down/feather and find the dust mite/allergy covers help a lot! They came from Target and are called Allerease. Maybe woth a try.

https://www.natlallergy.com/all-cotton-allergy-pillow-covers-1.html?ps=MjA2PTIxMw==&gad_source=1&gad_campaignid=22734766452&gbraid=0AAAAAD_nGxeHb3D-J9dGysK_uqzui7bTy&gclid=EAIaIQobChMIuKfq-M-MlwMV7n9vBB1jyh4GEAQYAiABEgJsNvD_BwE#206=213

Maybe your bed pillows need an upgrade beyond the cover? We tend to forget how long we've owned these?

Or even a good washing? Yes, I do wash mine, every four months, and they come out great.

There's a huge difference between goose down and feather down.

That said?

" Goose down is generally considered less likely to trigger allergies compared to feathers due to larger cluster sizes and higher purity, though true protein allergies to either are very rare. [1, 2]Key Differences Regarding Allergies

• Structure and Trapping: Feathers contain flat, rigid quills that can poke through fabric casings, potentially trapping dust, dander, and debris. Goose down consists of fluffy, 3D clusters without quills, making it easier to clean thoroughly and less prone to holding onto particulate matter when processed. [1]
• The Dust Mite Myth: Most allergic reactions attributed to feather or down bedding are actually caused by house dust mites, not the bird material itself. Studies show that tightly woven, "down-proof" casings used for quality down and feather products block dust mites better than many synthetic alternatives. [1, 2, 3]
• Processing and Purity: Premium goose down undergoes rigorous washing, rinsing, and high-heat sterilization to remove residual organic matter and dust. Because goose down clusters are larger and command a higher grade, they often receive more intensive purifying treatments and certifications like the Responsible Down Standard (RDS) or OEKO-TEX Standard 100. [1, 2, 3, 4]
• Direct Protein Sensitivity: A true allergy to bird proteins or residual dust on feathers/down is uncommon. However, breathing in fine organic dust from unwashed or deteriorating feather/down products can rarely cause a hypersensitivity reaction known as hypersensitivity pneumonitis."

Failing that? wash em!!

Step 1 - Wash in COLD water with a MILD detergent. Don’t use a scented laundry detergent or scented laundry beads. Perfumes have oils which latch onto the down and feathers and can cause a bad mildew smell later. My approved mild detergent s are as follows : ALL free and clear, ECOS Laundry Detergent, Seventh Generation Natural Laundry Detergent, and TIDE free and gentle. Stay away from laundry pods. Add an extra spin cycle to your wash if you have that setting. You want to wring out as much water as possible.

Step 2 - Dry on low heat with no scented dryer sheets. Add some clean tennis balls or dryer balls to help fluff the pillows while they are drying. Make sure to run the dryer for multiple drying cycles. It can take as many as 3-4 full drying cycles on low heat to have all the down and feathers fully dried. Be patient, this process takes a few hours but will ensure your pillows don’t get a bad odor. If you don’t fully dry the fill, it will create a bad odor from mold and mildew. Once a down and feather pillows has that bad odor, it can not be reversed.