Legumes, pulses, beans… Some terminology first: legumes are plants in family Fabaceae (or Leguminosae). Pulses are (strictly) those cultivated for DRY seed, as opposed to green beans, broad beans etc that are eaten fresh. Lentil simply describes shape (“like lens”). So other examples of legumes are peanut, lupin, tamarind, carob, alfalfa!
Very common cause of food allergy, even excluding peanut! And varies across different cultures, depending on typical pulses used. Fifth most common cause of food allergy in Spain. In India, often a trigger of asthma/rhinitis when being boiled. Cross sensitivity is seen, but not automatic, and hard to predict.
Soya allergy is sometimes seen in highly atopic babies, but otherwise actually pretty rare (except in Japan) – lucky, cause gets into lots of different things eg many breads. Soya lecithin is a common additive, used to make texture more smooth, but usually only in very small amounts.
Lupin is used in some continental baked goods, for example packaged waffles. A good proportion of peanut allergic children will be allergic to it too, but as lupin is not found very commonly most will never know or have a problem with it.
A couple of lentil allergens have been identified including a vicilin and a lipid transfer protein. In my experience pappadoms can often be tolerated – there is certainly evidence that autoclaving for 30 mins can affect binding, but these are only deep fried for a few seconds.
Both the known pea allergens are vicilins, hence cross reactivity with lentil. Chickpea allergens however are not (one a prolamin, the other a cupin) so you might not expect cross reactivity.
French beans have a LTP so rarely an issue. Green (mung bean) and red gram are cupins, black gram appears to be something else.[Clin Rev Allergy Immunol. 45(1):30-46, 2013 Aug]