Safety Study of MK-3641 and MK-7243 Co-administered in Adult Participants With Ragweed and Grass Pollen Induced Allergic Rhinitis (MK-3641-006)

Events of local swelling include pharyngeal edema, laryngeal edema, mouth edema,
oropharyngeal swelling, palatal edema, tongue swelling/edema or throat tightness.

Inclusion Criteria:

- Clinical history of physician-diagnosed ragweed- and grass pollen-induced rhinitis
with or without conjunctivitis of >1 year duration, with or without asthma

- Female participants of childbearing potential must have a negative urine pregnancy
test at Screening and Randomization Visits and must agree to remain abstinent or use
(or have their partner use) any one of the acceptable methods of birth control within
the projected duration of the study. Acceptable methods of birth control are:
intrauterine device (IUD), diaphragm with spermicide, contraceptive sponge, condom,
vasectomy, hormonal contraception.

Exclusion Criteria:

- Unstable, uncontrolled or severe asthma treated with long-acting beta agonists
(LABAs) at the time of Screening

- Received immunosuppressive treatment within 3 months prior to Randomization (except
steroids for allergic reactions other than asthma)

- History of anaphylaxis with cardiorespiratory symptoms with prior immunotherapy,
unknown cause, or inhalant allergen

- Diagnosis of eosinophilic esophagitis

- History of any severe systemic allergic reaction or any severe local reaction to
sublingual allergen immunotherapy

- Female and breastfeeding, pregnant or intending to become pregnant

- Received another form of allergen immunotherapy with the past month

- Previously exposed to MK-3641 (RAGWITEK®) or other sublingual ragweed immunotherapy

- Previously exposed to MK-7243 (GRASTEK®) or other sublingual grass immunotherapy

- Known history of allergy, hypersensitivity, or intolerance to the excipient
ingredients of the study drug (except for Ambrosia artemisiifolia and/or Phleum
pratense), or self-injectable epinephrine

- Unable to or will not comply with the use of self-injectable epinephrine

- Used an investigational drug within 30 days prior to Screening Visit, or plans to
participate in another interventional clinical trial during the duration of this
trial

- Family member of the investigational or sponsor staff involved in this trial

- Participating in this same trial at another investigational site.