I have read that carrageenan solution causes swelling/ oedema upon subcutaneous injection.

 

I was wondering, could it cause swelling/ oedema upon contact with mucous membranes such as the lining of the mouth/ respiratory tract, in high concentration?

Not the same way, though there may other complications, especially at high concentration. One thing is that it may be very rich in iodine, which could be a problem with sensitivity against it. There have been reports associating carrageenan with bowel and stomach issues but there is nothing definite, as far as I know. The problem with that is obviously that we have to rely on animal models, which may not represent humans conclusively.

Moreover, for any problems that are not acute and have a rare occurrence within a population it is often hard or impossible to deconvolute all the factors that are involved (i.e. other components of the diet, existing allergies, genetic disposition, life style etc.).

 

But going back to the question, it is not impossible, though it does not appear to happen frequently (at least with the dosages used as additives).

The swelling/edema is not what you should be concerned about considering that carrageenan is a cause of range of cancers.