Smelling Your Etrog
Although not widely known, it might actually be forbidden to smell one's etrog or hadassim on Sukkot. This is because when something is set aside specifically for a mitzva, it is often forbidden to make any other use of it whatsoever – including enjoying its fragrance. The Talmud rules that since the primary feature of the hadassim are their smell, it is forbidden to smell them while they are part of the lulav bundle on Sukkot. On the other hand, the primary feature of an etrog is its food value, and therefore, it may be permitted to smell it.
Nevertheless, the Shulchan Aruch recommends that one avoid smelling an etrog due to the uncertainty of whether or not a blessing should be recited before doing so. Although as a general rule, one is required to recite a blessing before enjoying fragrances, some authorities rule that a blessing should not be recited when smelling an Etrog on Sukkot. This is because the primary reason that one purchases an etrog before sukkot is in order to use it for the mitzva – not for its fragrance or even its food value. The blessing for pleasant fragrances is only recited upon an item whose primary feature is the smell it emits.
Others reject this approach, arguing that the requirement to recite a blessing before enjoying a pleasant fragrance overrides the concern that the primary use of an etrog is for a mitzva, and not for the pleasant scent it emits. According to those who permit one to smell an etrog on sukkot, the blessing one would recite before doing so is “….hanoten rei’ach tov bapeirot" (“…who gives a pleasant fragrances to fruits”). All authorities agree, however, that a blessing is not recited if one happens to smell one’s etrog in the course of shaking it along with the lulav.
Although the lulav bundle is muktza and may not be moved on Shabbat, the etrog itself is not muktza and may be smelled on Shabbat. There is an opinion that one who purchases hadassim for sukkot with the express intention of smelling them over sukkot -- in addition to using them for the mitzva -- is permitted to do so. Otherwise, smelling hadassim on sukkot is considered to be so severe that one who smells them forfeits the opportunity to recite a blessing on their fragrance before doing so.
 Sukka 37b; OC 653:1; Mishna Berura 653:1.
 OC 653:1; OC 216:14.
 OC 217:2,3.
 See Mishna Berura 216:52.
 OC 216:2.
 Mishna Berura 216:51.
 Mishna Berura 653:2.
 Piskei Teshuvot 216:14, note 88.