OK, basic question: what are the blankets made of? What does the fabric care tag say (with symbols) on it?

The answer to those questions will help you know if what you are doing is correct.

I'll answer your question as if the blankets were made of wool (including the so-called machine washable wool).

These instructions apply to the washing of any washable wool item. As a rule this would include any wool blanket, providing you can make sure to follow them to the letter, and never allow excess agitation or temps.

Use delicate cycle (always with wool). Cycle should be one with gentle action, long pauses for interim soaks and overall be shorter in time than regular cycles. If your only choice is regular cycle, then see if you can interrupt it to shorten it, or otherwise make it gentler in action. Sometimes it takes abit of fooling around to find the best cycle. I've even started the wash cycle in a top loader and waited to put my delicate items in until later on in the cycle to artificially shorten the wash period. You can avoid wasting the water and coins by experimenting with the machines while washing something else.

Use special detergent with wool (my preferences in order: Perwol powder, Eucalan liquid, Delicare liquid and Woolite liquid). Of these detergents Delicare and Woolite are the most easily available, Eucalan is available on Amazon and small bottle will serve you for a long time. Perwol powder is hardest to get. A little wool detergent goes long way, even for blankets in a machine, so plan on just a minimal amount; it's better to under-dose at first than over-dose.

(If you are using public machines with tons of accumulated detergent goop in the dispensers, clean them out before doing the blankets.)

Use cool/cold water for your first tries at washing wool; and never go above barely warm.

Use no fabric softener, except maybe some (1/4 cup or less in a top loader) white vinegar in the rinse cycle.

It's OK to spin the blankets (once fully drained of water) at higher speeds.

Do not machine dry wool unless the fabric care label specifically says this is OK (and use very low to no heat, always.) Line drying is always safer, and usually better. You don't need an actual line for this, sometimes several chairs can be set up to provide a drying platform over their backs.

Expect wool to feel a little scratchy right after it is dry. This is because wool fibers are actually arranged in a series of overlapping scales and the mechanical action of a water washing temprarily disturbs how smoothly they lie against one another. Given time and rest, the wool fibers will anneal themseleves and the "hand" of the fabric will improve, often quite dramatically.

Wool, when subject to moisture, temps and agitation will begin a process called felting, which is an irreversible change to a stiff, thick, texture. The goal in washing wool is to make the best cycle choices in order to minimize the temps and agitation to avoid precipitating any felting. I usually deliberately err on the side of insufficient cleaning vs. risking overheating or too-much agitation. You can always re-wash something, perhaps after a little spot treatment, if it turns out that it did not get clean enough in the first washing. But you can NOT undo the damage from over-aggressive cleaning. Wool also shrinks as it felts.

Wool is probably the most delicate of all possible blanket fibers. If your blankets have no tags, it's probably safe to use these instructions on all other fibers.

Also, blankets probably don't need to be washed very often unless you are sleeping in them w/o sheets, or they are subject to spills. Washing them a couple of times a year is generally fine. Sheets and bed coverlets (generally highly washable) serve not only to improve personal comfort, but can also take the brunt of the necessary cleaning.

HTH,

L.

Dry Clean Only? Fabric content and, to a lesser extent, the care label are your friends. If it's wool, it might be beyond saving. I've never seen something "unshrunk" though I have seen items blocked or methodically stretched somewhere close to original size.

Vinegar is good for many things but it's not generally a silver bullet.

OP, vinegar is not a fabric softener. It is an astringent and strips out any residual detergent when used in the final rinse. I love to use it when washing towels.

If your blanket is wool, I would be extra-careful and be sure to follow the guidelines given on its label(s). Wool does tend to be scratchy, at least for me; if I use a wool blanket, I have to have a nice soft sheet between it and me when I sleep.

They're both 100% cotton, sorry I forgot to mention this. After another wash with no detergent and a bit of softener they feel better. This time I washed them on a delicate cycle and dried on low heat. I removed the blankets when they were still a bit damp from the dryer and let them dry overnight. Now they don't feel itchy.

I know this is rather an old post but for the benefit of those who have just joined or found this post I offer this information.
Vinegar IS a fabric softener and is often use as such for those allergic to regular fabric softeners. It is also used in cooking as a tenderizer for meat, by the way.
What I learned as a weaver is this: I use Palmolive Original formula for woolens and delicate fabrics because it has a Ph that is friendly to fabrics. I have used it as shampoo when I run out just for this reason.
Woolens and linen and such need to be washed in TEPID, not warm, not cold, not lukewarm water. Extremes in temperature shock the fibers and this is what makes them shrink or warp.
Stong detergents are too harsh for woolens and other natural fibers. It washes out what is left of the natural oils in the fibers and virtually can ruin garments and blankets no matter the temperature. I never use Woolite.
That said, I have read blogs of people buying extra large blankets and washing them in the hottest possible water and drying at the highest temperature in the dryer with predictable results. Typically, there will be more shrinkage top to bottom or warp wise than weft wise (across or width) For most woolens it will shrink them up as far as they will shrink (subsequent washing will be easier and more predictable) and for some woolens it felts them. Many people like their blankets felted as this process can cause the blanket or clothing fibers to join closer together allowing less air to permeate the fabric. Thus, it is warmer and sheds less at the time of washing.
For those of you washing linen, use a mild detergent, I use Palmolive Original in a small amount in my washer for linen and wool. At the rinse cycle I use fabric softener or you can use vinegar (it won't smell when done) and you will have much less ironing to contend with. The more often linen is washed, the softer it gets and more beautiful it becomes so be patient with it.
By the Way, I follow this for woven fabrics only not knitted or crocheted. There is no warp or weft in these styles. All of this type of garment or blanket should be hand washed according to instructions if they are made from natural fibers such as Irish woolen sweaters. I have an afghan made from synthetic fibers and I just throw it in the wash on gentle cycle.