A hydrating makeup primer for dry skin is a specialized base coat designed to provide an extra layer of moisture, smoothing rough texture, and preventing foundation from clinging to dry patches. It acts as a bridge between skincare and makeup, often containing ingredients like hyaluronic acid, shea butter, or glycerin to ensure a dewy, plump finish that lasts all day. 
Key Aspects of Hydrating Primers for Dry Skin
Hydration Boost: These primers are specifically formulated to combat dryness and flakiness, providing a surge of moisture to parched skin.
Smooth Canvas: They help in filling in fine lines and smoothing the skin surface, ensuring makeup glides on easily and does not settle into creases.
Long-Lasting Wear: By keeping the skin hydrated, these primers prevent foundation from separating or looking cakey, helping makeup stay fresh and vibrant.
Key Ingredients: Look for formulas containing hyaluronic acid (for deep hydration), glycerin (to lock in moisture), ceramides (to strengthen the skin barrier), and vitamin E or aloe vera (for nourishment).
Texture: They usually have a lotion, serum, or cream-like consistency rather than a heavy silicone feel. 
Popular Options in the Market
Flicka Silk Touch Priming Moisturizer: Infused with shea butter, vitamin C, and aloe vera, this 3-in-1 product hydrates and primes.
MARS Hydra Glow Primer: Features hyaluronic acid and argan oil to nourish skin for a dewy radiance.
Too Faced Hangover Replenishing Face Primer: Contains coconut water and probiotics for a refreshed appearance.
Smashbox Photo Finish Primerizer+: A primer and moisturizer hybrid that offers up to 72-hour hydration.